The first 40 odd counting numbers are written how many times does 3 appear as a digit
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I faced this problem on one test. I wrote my solution but then I found out that my solution is wrong, I still cannot find where my mistake is. Show
The problem says: How many three-digits numbers are there such that they are odd and their digits are all different. Here is my approach: We have three digits. Since the number should be odd, the last digit should be one of those numbers $1, 3, 5, 7, 9$. Now the second digits can be one of the digits: $0, 1, 2, 3, 4, 5, 6, 7, 8, 9$ There are 10 different digits for the second digits, but since the digits should be different we cannot place 10 digits, but we can place 9 digits. And for the first digits we can place digits in the range $1...9$ but we cannot place the digits that are used in the two other digits and we can place only 7 digits. So my result is $7\cdot9\cdot5 = 315$ However the result is not correct, because there are $320$ odd three-digits numbers with different digits. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”. 1 Introductionsed -i 's/hello/world/' file.txt22 is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). While in some ways similar to an editor which permits scripted edits (such as sed -i 's/hello/world/' file.txt24), sed -i 's/hello/world/' file.txt22 works by making only one pass over the input(s), and is consequently more efficient. But it is sed -i 's/hello/world/' file.txt22’s ability to filter text in a pipeline which particularly distinguishes it from other types of editors. 2 Running sedThis chapter covers how to run sed -i 's/hello/world/' file.txt22. Details of sed -i 's/hello/world/' file.txt22 scripts and individual sed -i 's/hello/world/' file.txt22 commands are discussed in the next chapter. 2.1 OverviewNormally sed -i 's/hello/world/' file.txt22 is invoked like this: For example, to replace all occurrences of ‘hello’ to ‘world’ in the file input.txt: sed 's/hello/world/' input.txt > output.txt If you do not specify INPUTFILE, or if INPUTFILE is -, sed -i 's/hello/world/' file.txt22 filters the contents of the standard input. The following commands are equivalent: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt sed -i 's/hello/world/' file.txt22 writes output to standard output. Use -i to edit files in-place instead of printing to standard output. See also the sed -i 's/hello/world/' file.txt33 and sed -i 's/hello/world/' file.txt34 commands for writing output to other files. The following command modifies file.txt and does not produce any output: sed -i 's/hello/world/' file.txt By default sed -i 's/hello/world/' file.txt22 prints all processed input (except input that has been modified/deleted by commands such as sed -i 's/hello/world/' file.txt36). Use -n to suppress output, and the sed -i 's/hello/world/' file.txt37 command to print specific lines. The following command prints only line 45 of the input file: sed -i 's/hello/world/' file.txt22 treats multiple input files as one long stream. The following example prints the first line of the first file (one.txt) and the last line of the last file (three.txt). Use -s to reverse this behavior. sed -n '1p ; $p' one.txt two.txt three.txt Without -e or -f options, sed -i 's/hello/world/' file.txt22 uses the first non-option parameter as the script, and the following non-option parameters as input files. If -e or -f options are used to specify a script, all non-option parameters are taken as input files. Options -e and -f can be combined, and can appear multiple times (in which case the final effective script will be concatenation of all the individual scripts). The following examples are equivalent: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt 2.2 Command-Line OptionsThe full format for invoking sed -i 's/hello/world/' file.txt22 is: sed OPTIONS... [SCRIPT] [INPUTFILE...] sed -i 's/hello/world/' file.txt22 may be invoked with the following command-line options: sed -i 's/hello/world/' file.txt42 Print out the version of sed -i 's/hello/world/' file.txt22 that is being run and a copyright notice, then exit. sed -i 's/hello/world/' file.txt44 Print a usage message briefly summarizing these command-line options and the bug-reporting address, then exit. sed -i 's/hello/world/' file.txt45 sed -i 's/hello/world/' file.txt46 sed -i 's/hello/world/' file.txt47 By default, sed -i 's/hello/world/' file.txt22 prints out the pattern space at the end of each cycle through the script (see How sed -i 's/hello/world/' file.txt22 works). These options disable this automatic printing, and sed -i 's/hello/world/' file.txt22 only produces output when explicitly told to via the sed -i 's/hello/world/' file.txt37 command. sed -i 's/hello/world/' file.txt52 Print the input sed program in canonical form, and annotate program execution. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 3 sed -i 's/hello/world/' file.txt53 sed -i 's/hello/world/' file.txt54 Add the commands in script to the set of commands to be run while processing the input. sed -i 's/hello/world/' file.txt55 sed -i 's/hello/world/' file.txt56 Add the commands contained in the file script-file to the set of commands to be run while processing the input. sed -i 's/hello/world/' file.txt57 sed -i 's/hello/world/' file.txt58 This option specifies that files are to be edited in-place. GNU sed -i 's/hello/world/' file.txt22 does this by creating a temporary file and sending output to this file rather than to the standard output.1. This option implies -s. When the end of the file is reached, the temporary file is renamed to the output file’s original name. The extension, if supplied, is used to modify the name of the old file before renaming the temporary file, thereby making a backup copy2). This rule is followed: if the extension doesn’t contain a sed -i 's/hello/world/' file.txt60, then it is appended to the end of the current filename as a suffix; if the extension does contain one or more sed -i 's/hello/world/' file.txt60 characters, then each asterisk is replaced with the current filename. This allows you to add a prefix to the backup file, instead of (or in addition to) a suffix, or even to place backup copies of the original files into another directory (provided the directory already exists). If no extension is supplied, the original file is overwritten without making a backup. Because -i takes an optional argument, it should not be followed by other short options: sed -i 's/hello/world/' file.txt62 Same as -E -i with no backup suffix - FILE will be edited in-place without creating a backup. sed -i 's/hello/world/' file.txt63 This is equivalent to --in-place=E, creating FILEE as backup of FILE Be cautious of using -n with -i: the former disables automatic printing of lines and the latter changes the file in-place without a backup. Used carelessly (and without an explicit sed -i 's/hello/world/' file.txt37 command), the output file will be empty: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE sed -i 's/hello/world/' file.txt65 sed -i 's/hello/world/' file.txt66 Specify the default line-wrap length for the sed -i 's/hello/world/' file.txt67 command. A length of 0 (zero) means to never wrap long lines. If not specified, it is taken to be 70. sed -i 's/hello/world/' file.txt68 GNU sed -i 's/hello/world/' file.txt22 includes several extensions to POSIX sed. In order to simplify writing portable scripts, this option disables all the extensions that this manual documents, including additional commands. Most of the extensions accept sed -i 's/hello/world/' file.txt22 programs that are outside the syntax mandated by POSIX, but some of them (such as the behavior of the sed -i 's/hello/world/' file.txt71 command described in Reporting Bugs) actually violate the standard. If you want to disable only the latter kind of extension, you can set the sed -i 's/hello/world/' file.txt72 variable to a non-empty value. sed -i 's/hello/world/' file.txt73 sed -i 's/hello/world/' file.txt74 This option is available on every platform, but is only effective where the operating system makes a distinction between text files and binary files. When such a distinction is made—as is the case for MS-DOS, Windows, Cygwin—text files are composed of lines separated by a carriage return and a line feed character, and sed -i 's/hello/world/' file.txt22 does not see the ending CR. When this option is specified, sed -i 's/hello/world/' file.txt22 will open input files in binary mode, thus not requesting this special processing and considering lines to end at a line feed. sed -i 's/hello/world/' file.txt77 This option is available only on platforms that support symbolic links and has an effect only if option -i is specified. In this case, if the file that is specified on the command line is a symbolic link, sed -i 's/hello/world/' file.txt22 will follow the link and edit the ultimate destination of the link. The default behavior is to break the symbolic link, so that the link destination will not be modified. sed -i 's/hello/world/' file.txt79 sed -i 's/hello/world/' file.txt80 sed -i 's/hello/world/' file.txt81 Use extended regular expressions rather than basic regular expressions. Extended regexps are those that sed -i 's/hello/world/' file.txt82 accepts; they can be clearer because they usually have fewer backslashes. Historically this was a GNU extension, but the -E extension has since been added to the POSIX standard (http://austingroupbugs.net/view.php?id=528), so use -E for portability. GNU sed has accepted -E as an undocumented option for years, and *BSD seds have accepted -E for years as well, but scripts that use -E might not port to other older systems. See Extended regular expressions. sed -i 's/hello/world/' file.txt83 sed -i 's/hello/world/' file.txt84 By default, sed -i 's/hello/world/' file.txt22 will consider the files specified on the command line as a single continuous long stream. This GNU sed -i 's/hello/world/' file.txt22 extension allows the user to consider them as separate files: range addresses (such as ‘/abc/,/def/’) are not allowed to span several files, line numbers are relative to the start of each file, sed -i 's/hello/world/' file.txt87 refers to the last line of each file, and files invoked from the sed -i 's/hello/world/' file.txt88 commands are rewound at the start of each file. sed -i 's/hello/world/' file.txt89 In sandbox mode, sed -i 's/hello/world/' file.txt90 commands are rejected - programs containing them will be aborted without being run. Sandbox mode ensures sed -i 's/hello/world/' file.txt22 operates only on the input files designated on the command line, and cannot run external programs. sed -i 's/hello/world/' file.txt92 sed -i 's/hello/world/' file.txt93 Buffer both input and output as minimally as practical. (This is particularly useful if the input is coming from the likes of ‘tail -f’, and you wish to see the transformed output as soon as possible.) sed -i 's/hello/world/' file.txt94 sed -i 's/hello/world/' file.txt95 sed -i 's/hello/world/' file.txt96 Treat the input as a set of lines, each terminated by a zero byte (the ASCII ‘NUL’ character) instead of a newline. This option can be used with commands like ‘sort -z’ and ‘find -print0’ to process arbitrary file names. If no -e, -f, --expression, or --file options are given on the command-line, then the first non-option argument on the command line is taken to be the script to be executed. If any command-line parameters remain after processing the above, these parameters are interpreted as the names of input files to be processed. A file name of ‘-’ refers to the standard input stream. The standard input will be processed if no file names are specified. 2.3 Exit statusAn exit status of zero indicates success, and a nonzero value indicates failure. GNU sed -i 's/hello/world/' file.txt22 returns the following exit status error values:0 Successful completion. 1Invalid command, invalid syntax, invalid regular expression or a GNU sed -i 's/hello/world/' file.txt22 extension command used with --posix.2 One or more of the input file specified on the command line could not be opened (e.g. if a file is not found, or read permission is denied). Processing continued with other files. 4An I/O error, or a serious processing error during runtime, GNU sed -i 's/hello/world/' file.txt22 aborted immediately. Additionally, the commands sed -n '1p ; $p' one.txt two.txt three.txt00 and sed -n '1p ; $p' one.txt two.txt three.txt01 can be used to terminate sed -i 's/hello/world/' file.txt22 with a custom exit code value (this is a GNU sed -i 's/hello/world/' file.txt22 extension): $ echo | sed 'Q42' ; echo $? 42 3 sed -i 's/hello/world/' file.txt 22 scripts3.1 sed -i 's/hello/world/' file.txt 22 script overviewA sed -i 's/hello/world/' file.txt22 program consists of one or more sed -i 's/hello/world/' file.txt22 commands, passed in by one or more of the -e, -f, --expression, and --file options, or the first non-option argument if zero of these options are used. This document will refer to “the” sed -i 's/hello/world/' file.txt22 script; this is understood to mean the in-order concatenation of all of the scripts and script-files passed in. See Overview. sed -i 's/hello/world/' file.txt22 commands follow this syntax: X is a single-letter sed -i 's/hello/world/' file.txt22 command. sed -n '1p ; $p' one.txt two.txt three.txt11 is an optional line address. If sed -n '1p ; $p' one.txt two.txt three.txt11 is specified, the command X will be executed only on the matched lines. sed -n '1p ; $p' one.txt two.txt three.txt11 can be a single line number, a regular expression, or a range of lines (see sed addresses). Additional sed -n '1p ; $p' one.txt two.txt three.txt14 are used for some sed -i 's/hello/world/' file.txt22 commands. The following example deletes lines 30 to 35 in the input. sed -n '1p ; $p' one.txt two.txt three.txt16 is an address range. sed -i 's/hello/world/' file.txt36 is the delete command: sed '30,35d' input.txt > output.txt The following example prints all input until a line starting with the word ‘foo’ is found. If such line is found, sed -i 's/hello/world/' file.txt22 will terminate with exit status 42. If such line was not found (and no other error occurred), sed -i 's/hello/world/' file.txt22 will exit with status 0. sed -n '1p ; $p' one.txt two.txt three.txt20 is a regular-expression address. sed -n '1p ; $p' one.txt two.txt three.txt00 is the quit command. sed -n '1p ; $p' one.txt two.txt three.txt22 is the command option. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt0 Commands within a script or script-file can be separated by semicolons ( sed -n '1p ; $p' one.txt two.txt three.txt23) or newlines (ASCII 10). Multiple scripts can be specified with -e or -f options. The following examples are all equivalent. They perform two sed -i 's/hello/world/' file.txt22 operations: deleting any lines matching the regular expression sed -n '1p ; $p' one.txt two.txt three.txt20, and replacing all occurrences of the string ‘hello’ with ‘world’: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt1 Commands sed -n '1p ; $p' one.txt two.txt three.txt26, sed -n '1p ; $p' one.txt two.txt three.txt27, sed -n '1p ; $p' one.txt two.txt three.txt28, due to their syntax, cannot be followed by semicolons working as command separators and thus should be terminated with newlines or be placed at the end of a script or script-file. Commands can also be preceded with optional non-significant whitespace characters. See Multiple commands syntax. 3.2 sed -i 's/hello/world/' file.txt 22 commands summaryThe following commands are supported in GNU sed -i 's/hello/world/' file.txt22. Some are standard POSIX commands, while other are GNU extensions. Details and examples for each command are in the following sections. (Mnemonics) are shown in parentheses. sed -n '1p ; $p' one.txt two.txt three.txt31 sed -n '1p ; $p' one.txt two.txt three.txt32 Append text after a line. sed -n '1p ; $p' one.txt two.txt three.txt33 Append text after a line (alternative syntax). sed -n '1p ; $p' one.txt two.txt three.txt34 Branch unconditionally to label. The label may be omitted, in which case the next cycle is started. sed -n '1p ; $p' one.txt two.txt three.txt35 sed -n '1p ; $p' one.txt two.txt three.txt32 Replace (change) lines with text. sed -n '1p ; $p' one.txt two.txt three.txt37 Replace (change) lines with text (alternative syntax). sed -i 's/hello/world/' file.txt36 Delete the pattern space; immediately start next cycle. sed -n '1p ; $p' one.txt two.txt three.txt39 If pattern space contains newlines, delete text in the pattern space up to the first newline, and restart cycle with the resultant pattern space, without reading a new line of input. If pattern space contains no newline, start a normal new cycle as if the sed -i 's/hello/world/' file.txt36 command was issued. sed -n '1p ; $p' one.txt two.txt three.txt41 Executes the command that is found in pattern space and replaces the pattern space with the output; a trailing newline is suppressed. sed -n '1p ; $p' one.txt two.txt three.txt42 Executes command and sends its output to the output stream. The command can run across multiple lines, all but the last ending with a back-slash. sed -n '1p ; $p' one.txt two.txt three.txt43 (filename) Print the file name of the current input file (with a trailing newline). sed -n '1p ; $p' one.txt two.txt three.txt44 Replace the contents of the pattern space with the contents of the hold space. sed -n '1p ; $p' one.txt two.txt three.txt45 Append a newline to the contents of the pattern space, and then append the contents of the hold space to that of the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt46 (hold) Replace the contents of the hold space with the contents of the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt47 Append a newline to the contents of the hold space, and then append the contents of the pattern space to that of the hold space. sed -n '1p ; $p' one.txt two.txt three.txt48 sed -n '1p ; $p' one.txt two.txt three.txt32 insert text before a line. sed -n '1p ; $p' one.txt two.txt three.txt50 insert text before a line (alternative syntax). sed -i 's/hello/world/' file.txt67 Print the pattern space in an unambiguous form. sed -n '1p ; $p' one.txt two.txt three.txt52 (next) If auto-print is not disabled, print the pattern space, then, regardless, replace the pattern space with the next line of input. If there is no more input then sed -i 's/hello/world/' file.txt22 exits without processing any more commands. sed -i 's/hello/world/' file.txt71 Add a newline to the pattern space, then append the next line of input to the pattern space. If there is no more input then sed -i 's/hello/world/' file.txt22 exits without processing any more commands. sed -i 's/hello/world/' file.txt37 Print the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt57 Print the pattern space, up to the first. sed -n '1p ; $p' one.txt two.txt three.txt58 (quit) Exit sed -i 's/hello/world/' file.txt22 without processing any more commands or input. sed -n '1p ; $p' one.txt two.txt three.txt60 (quit) This command is the same as sed -n '1p ; $p' one.txt two.txt three.txt00, but will not print the contents of pattern space. Like sed -n '1p ; $p' one.txt two.txt three.txt00, it provides the ability to return an exit code to the caller. sed -n '1p ; $p' one.txt two.txt three.txt63 Reads file filename. sed -n '1p ; $p' one.txt two.txt three.txt64 Queue a line of filename to be read and inserted into the output stream at the end of the current cycle, or when the next input line is read. sed -n '1p ; $p' one.txt two.txt three.txt65 (substitute) Match the regular-expression against the content of the pattern space. If found, replace matched string with replacement. sed -n '1p ; $p' one.txt two.txt three.txt66 (test) Branch to label only if there has been a successful sed -n '1p ; $p' one.txt two.txt three.txt67ubstitution since the last input line was read or conditional branch was taken. The label may be omitted, in which case the next cycle is started. sed -n '1p ; $p' one.txt two.txt three.txt68 (test) Branch to label only if there have been no successful sed -n '1p ; $p' one.txt two.txt three.txt67ubstitutions since the last input line was read or conditional branch was taken. The label may be omitted, in which case the next cycle is started. sed -n '1p ; $p' one.txt two.txt three.txt70 (version) This command does nothing, but makes sed -i 's/hello/world/' file.txt22 fail if GNU sed -i 's/hello/world/' file.txt22 extensions are not supported, or if the requested version is not available. sed -n '1p ; $p' one.txt two.txt three.txt73 Write the pattern space to filename. sed -n '1p ; $p' one.txt two.txt three.txt74 Write to the given filename the portion of the pattern space up to the first newline sed -n '1p ; $p' one.txt two.txt three.txt75 Exchange the contents of the hold and pattern spaces. sed -n '1p ; $p' one.txt two.txt three.txt76 Transliterate any characters in the pattern space which match any of the source-chars with the corresponding character in dest-chars. sed -n '1p ; $p' one.txt two.txt three.txt77 (zap) This command empties the content of pattern space. sed -n '1p ; $p' one.txt two.txt three.txt78 A comment, until the next newline. sed -n '1p ; $p' one.txt two.txt three.txt79 Group several commands together. sed -n '1p ; $p' one.txt two.txt three.txt80 Print the current input line number (with a trailing newline). sed -n '1p ; $p' one.txt two.txt three.txt81 Specify the location of label for branch commands ( sed -n '1p ; $p' one.txt two.txt three.txt82, sed -n '1p ; $p' one.txt two.txt three.txt83, sed -n '1p ; $p' one.txt two.txt three.txt84). 3.3 The sed -n '1p ; $p' one.txt two.txt three.txt 67 CommandThe sed -n '1p ; $p' one.txt two.txt three.txt67 command (as in substitute) is probably the most important in sed -i 's/hello/world/' file.txt22 and has a lot of different options. The syntax of the sed -n '1p ; $p' one.txt two.txt three.txt67 command is ‘s/regexp/replacement/flags’. Its basic concept is simple: the sed -n '1p ; $p' one.txt two.txt three.txt67 command attempts to match the pattern space against the supplied regular expression regexp; if the match is successful, then that portion of the pattern space which was matched is replaced with replacement. For details about regexp syntax see Regular Expression Addresses. The replacement can contain sed -n '1p ; $p' one.txt two.txt three.txt90 (n being a number from 1 to 9, inclusive) references, which refer to the portion of the match which is contained between the nth sed -n '1p ; $p' one.txt two.txt three.txt91 and its matching sed -n '1p ; $p' one.txt two.txt three.txt92. Also, the replacement can contain unescaped sed -n '1p ; $p' one.txt two.txt three.txt93 characters which reference the whole matched portion of the pattern space. The sed -n '1p ; $p' one.txt two.txt three.txt94 characters may be uniformly replaced by any other single character within any given sed -n '1p ; $p' one.txt two.txt three.txt67 command. The sed -n '1p ; $p' one.txt two.txt three.txt94 character (or whatever other character is used in its stead) can appear in the regexp or replacement only if it is preceded by a sed -n '1p ; $p' one.txt two.txt three.txt97 character. Finally, as a GNU sed -i 's/hello/world/' file.txt22 extension, you can include a special sequence made of a backslash and one of the letters sed -n '1p ; $p' one.txt two.txt three.txt99, sed -i 's/hello/world/' file.txt67, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt01, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt02, or sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt03. The meaning is as follows: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt04 Turn the replacement to lowercase until a sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt05 or sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt06 is found, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt07 Turn the next character to lowercase, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt05 Turn the replacement to uppercase until a sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt04 or sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt06 is found, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt11 Turn the next character to uppercase, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt06 Stop case conversion started by sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt04 or sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt05. When the sed -n '1p ; $p' one.txt two.txt three.txt44 flag is being used, case conversion does not propagate from one occurrence of the regular expression to another. For example, when the following command is executed with ‘a-b-’ in pattern space: the output is ‘axxB’. When replacing the first ‘-’, the ‘\u’ sequence only affects the empty replacement of ‘\1’. It does not affect the sed -n '1p ; $p' one.txt two.txt three.txt75 character that is added to pattern space when replacing sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt17 with sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt18. On the other hand, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt07 and sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt11 do affect the remainder of the replacement text if they are followed by an empty substitution. With ‘a-b-’ in pattern space, the following command: will replace ‘-’ with ‘X’ (uppercase) and ‘b-’ with ‘Bx’. If this behavior is undesirable, you can prevent it by adding a ‘\E’ sequence—after ‘\1’ in this case. To include a literal sed -n '1p ; $p' one.txt two.txt three.txt97, sed -n '1p ; $p' one.txt two.txt three.txt93, or newline in the final replacement, be sure to precede the desired sed -n '1p ; $p' one.txt two.txt three.txt97, sed -n '1p ; $p' one.txt two.txt three.txt93, or newline in the replacement with a sed -n '1p ; $p' one.txt two.txt three.txt97. The sed -n '1p ; $p' one.txt two.txt three.txt67 command can be followed by zero or more of the following flags: sed -n '1p ; $p' one.txt two.txt three.txt44 Apply the replacement to all matches to the regexp, not just the first. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt28 Only replace the numberth match of the regexp. interaction in sed -n '1p ; $p' one.txt two.txt three.txt67 command Note: the POSIX standard does not specify what should happen when you mix the sed -n '1p ; $p' one.txt two.txt three.txt44 and number modifiers, and currently there is no widely agreed upon meaning across sed -i 's/hello/world/' file.txt22 implementations. For GNU sed -i 's/hello/world/' file.txt22, the interaction is defined to be: ignore matches before the numberth, and then match and replace all matches from the numberth on. sed -i 's/hello/world/' file.txt37 If the substitution was made, then print the new pattern space. Note: when both the sed -i 's/hello/world/' file.txt37 and sed -n '1p ; $p' one.txt two.txt three.txt41 options are specified, the relative ordering of the two produces very different results. In general, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt36 (evaluate then print) is what you want, but operating the other way round can be useful for debugging. For this reason, the current version of GNU sed -i 's/hello/world/' file.txt22 interprets specially the presence of sed -i 's/hello/world/' file.txt37 options both before and after sed -n '1p ; $p' one.txt two.txt three.txt41, printing the pattern space before and after evaluation, while in general flags for the sed -n '1p ; $p' one.txt two.txt three.txt67 command show their effect just once. This behavior, although documented, might change in future versions. sed -n '1p ; $p' one.txt two.txt three.txt73 If the substitution was made, then write out the result to the named file. As a GNU sed -i 's/hello/world/' file.txt22 extension, two special values of filename are supported: /dev/stderr, which writes the result to the standard error, and /dev/stdout, which writes to the standard output.3 sed -n '1p ; $p' one.txt two.txt three.txt41 This command allows one to pipe input from a shell command into pattern space. If a substitution was made, the command that is found in pattern space is executed and pattern space is replaced with its output. A trailing newline is suppressed; results are undefined if the command to be executed contains a NUL character. This is a GNU sed -i 's/hello/world/' file.txt22 extension. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt45 sed -n '1p ; $p' one.txt two.txt three.txt28 The sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt45 modifier to regular-expression matching is a GNU extension which makes sed -i 's/hello/world/' file.txt22 match regexp in a case-insensitive manner. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt49 sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt50 The sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt49 modifier to regular-expression matching is a GNU sed -i 's/hello/world/' file.txt22 extension which directs GNU sed -i 's/hello/world/' file.txt22 to match the regular expression in multi-line mode. The modifier causes sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 and sed -i 's/hello/world/' file.txt87 to match respectively (in addition to the normal behavior) the empty string after a newline, and the empty string before a newline. There are special character sequences ( sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt56 and sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt57) which always match the beginning or the end of the buffer. In addition, the period character does not match a new-line character in multi-line mode. 3.4 Often-Used CommandsIf you use sed -i 's/hello/world/' file.txt22 at all, you will quite likely want to know these commands. sed -n '1p ; $p' one.txt two.txt three.txt78 [No addresses allowed.] The sed -n '1p ; $p' one.txt two.txt three.txt78 character begins a comment; the comment continues until the next newline. If you are concerned about portability, be aware that some implementations of sed -i 's/hello/world/' file.txt22 (which are not POSIX conforming) may only support a single one-line comment, and then only when the very first character of the script is a sed -n '1p ; $p' one.txt two.txt three.txt78. Warning: if the first two characters of the sed -i 's/hello/world/' file.txt22 script are sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt64, then the -n (no-autoprint) option is forced. If you want to put a comment in the first line of your script and that comment begins with the letter ‘n’ and you do not want this behavior, then be sure to either use a capital ‘N’, or place at least one space before the ‘n’. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt65 Exit sed -i 's/hello/world/' file.txt22 without processing any more commands or input. Example: stop after printing the second line: This command accepts only one address. Note that the current pattern space is printed if auto-print is not disabled with the -n options. The ability to return an exit code from the sed -i 's/hello/world/' file.txt22 script is a GNU sed -i 's/hello/world/' file.txt22 extension. See also the GNU sed -i 's/hello/world/' file.txt22 extension sed -n '1p ; $p' one.txt two.txt three.txt01 command which quits silently without printing the current pattern space. sed -i 's/hello/world/' file.txt36 Delete the pattern space; immediately start next cycle. Example: delete the second input line: sed -i 's/hello/world/' file.txt37 Print out the pattern space (to the standard output). This command is usually only used in conjunction with the -n command-line option. Example: print only the second input line: sed -n '1p ; $p' one.txt two.txt three.txt52 If auto-print is not disabled, print the pattern space, then, regardless, replace the pattern space with the next line of input. If there is no more input then sed -i 's/hello/world/' file.txt22 exits without processing any more commands. This command is useful to skip lines (e.g. process every Nth line). Example: perform substitution on every 3rd line (i.e. two sed -n '1p ; $p' one.txt two.txt three.txt52 commands skip two lines): sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt2 GNU sed -i 's/hello/world/' file.txt22 provides an extension address syntax of first~step to achieve the same result: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt3 sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt77 A group of commands may be enclosed between sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt78 and sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt79 characters. This is particularly useful when you want a group of commands to be triggered by a single address (or address-range) match. Example: perform substitution then print the second input line: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt4 3.5 Less Frequently-Used CommandsThough perhaps less frequently used than those in the previous section, some very small yet useful sed -i 's/hello/world/' file.txt22 scripts can be built with these commands. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt81 Transliterate any characters in the pattern space which match any of the source-chars with the corresponding character in dest-chars. Example: transliterate ‘a-j’ into ‘0-9’: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt5 (The sed -n '1p ; $p' one.txt two.txt three.txt94 characters may be uniformly replaced by any other single character within any given sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt83 command.) Instances of the sed -n '1p ; $p' one.txt two.txt three.txt94 (or whatever other character is used in its stead), sed -n '1p ; $p' one.txt two.txt three.txt97, or newlines can appear in the source-chars or dest-chars lists, provide that each instance is escaped by a sed -n '1p ; $p' one.txt two.txt three.txt97. The source-chars and dest-chars lists must contain the same number of characters (after de-escaping). See the sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt87 command from GNU coreutils for similar functionality. sed -n '1p ; $p' one.txt two.txt three.txt33 Appending text after a line. This is a GNU extension to the standard sed -n '1p ; $p' one.txt two.txt three.txt26 command - see below for details. Example: Add the word ‘hello’ after the second line: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt6 Leading whitespace after the sed -n '1p ; $p' one.txt two.txt three.txt26 command is ignored. The text to add is read until the end of the line. sed -n '1p ; $p' one.txt two.txt three.txt31 sed -n '1p ; $p' one.txt two.txt three.txt32 Appending text after a line. Example: Add ‘hello’ after the second line (-| indicates printed output lines): sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt7 The sed -n '1p ; $p' one.txt two.txt three.txt26 command queues the lines of text which follow this command (each but the last ending with a sed -n '1p ; $p' one.txt two.txt three.txt97, which are removed from the output) to be output at the end of the current cycle, or when the next input line is read. As a GNU extension, this command accepts two addresses. Escape sequences in text are processed, so you should use sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt95 in text to print a single backslash. The commands resume after the last line without a backslash ( sed -n '1p ; $p' one.txt two.txt three.txt97) - ‘world’ in the following example: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt8 As a GNU extension, the sed -n '1p ; $p' one.txt two.txt three.txt26 command and text can be separated into two sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt98 parameters, enabling easier scripting: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt9 sed -n '1p ; $p' one.txt two.txt three.txt50 insert text before a line. This is a GNU extension to the standard sed -n '1p ; $p' one.txt two.txt three.txt28 command - see below for details. Example: Insert the word ‘hello’ before the second line: sed -i 's/hello/world/' file.txt0 Leading whitespace after the sed -n '1p ; $p' one.txt two.txt three.txt28 command is ignored. The text to add is read until the end of the line. sed -n '1p ; $p' one.txt two.txt three.txt48 sed -n '1p ; $p' one.txt two.txt three.txt32 Immediately output the lines of text which follow this command. Example: Insert ‘hello’ before the second line (-| indicates printed output lines): sed -i 's/hello/world/' file.txt1 As a GNU extension, this command accepts two addresses. Escape sequences in text are processed, so you should use sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt95 in text to print a single backslash. The commands resume after the last line without a backslash ( sed -n '1p ; $p' one.txt two.txt three.txt97) - ‘world’ in the following example: sed -i 's/hello/world/' file.txt2 As a GNU extension, the sed -n '1p ; $p' one.txt two.txt three.txt28 command and text can be separated into two sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt98 parameters, enabling easier scripting: sed -i 's/hello/world/' file.txt3 sed -n '1p ; $p' one.txt two.txt three.txt37 Replaces the line(s) with text. This is a GNU extension to the standard sed -n '1p ; $p' one.txt two.txt three.txt27 command - see below for details. Example: Replace the 2nd to 9th lines with the word ‘hello’: sed -i 's/hello/world/' file.txt4 Leading whitespace after the sed -n '1p ; $p' one.txt two.txt three.txt27 command is ignored. The text to add is read until the end of the line. sed -n '1p ; $p' one.txt two.txt three.txt35 sed -n '1p ; $p' one.txt two.txt three.txt32 Delete the lines matching the address or address-range, and output the lines of text which follow this command. Example: Replace 2nd to 4th lines with the words ‘hello’ and ‘world’ (-| indicates printed output lines): sed -i 's/hello/world/' file.txt5 If no addresses are given, each line is replaced. A new cycle is started after this command is done, since the pattern space will have been deleted. In the following example, the sed -n '1p ; $p' one.txt two.txt three.txt27 starts a new cycle and the substitution command is not performed on the replaced text: sed -i 's/hello/world/' file.txt6 As a GNU extension, the sed -n '1p ; $p' one.txt two.txt three.txt27 command and text can be separated into two sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt98 parameters, enabling easier scripting: sed -i 's/hello/world/' file.txt7 sed -n '1p ; $p' one.txt two.txt three.txt80 Print out the current input line number (with a trailing newline). sed -i 's/hello/world/' file.txt8 As a GNU extension, this command accepts two addresses. sed OPTIONS... [SCRIPT] [INPUTFILE...]17 Print the pattern space in an unambiguous form: non-printable characters (and the sed -n '1p ; $p' one.txt two.txt three.txt97 character) are printed in C-style escaped form; long lines are split, with a trailing sed -n '1p ; $p' one.txt two.txt three.txt97 character to indicate the split; the end of each line is marked with a sed -i 's/hello/world/' file.txt87. n specifies the desired line-wrap length; a length of 0 (zero) means to never wrap long lines. If omitted, the default as specified on the command line is used. The n parameter is a GNU sed -i 's/hello/world/' file.txt22 extension. sed -n '1p ; $p' one.txt two.txt three.txt63 Reads file filename. Example: sed -i 's/hello/world/' file.txt9 Queue the contents of filename to be read and inserted into the output stream at the end of the current cycle, or when the next input line is read. Note that if filename cannot be read, it is treated as if it were an empty file, without any error indication. As a GNU sed -i 's/hello/world/' file.txt22 extension, the special value /dev/stdin is supported for the file name, which reads the contents of the standard input. As a GNU extension, this command accepts two addresses. The file will then be reread and inserted on each of the addressed lines. sed -n '1p ; $p' one.txt two.txt three.txt73 Write the pattern space to filename. As a GNU sed -i 's/hello/world/' file.txt22 extension, two special values of filename are supported: /dev/stderr, which writes the result to the standard error, and /dev/stdout, which writes to the standard output.4 The file will be created (or truncated) before the first input line is read; all sed OPTIONS... [SCRIPT] [INPUTFILE...]26 commands (including instances of the sed OPTIONS... [SCRIPT] [INPUTFILE...]26 flag on successful sed -n '1p ; $p' one.txt two.txt three.txt67 commands) which refer to the same filename are output without closing and reopening the file. sed -n '1p ; $p' one.txt two.txt three.txt39 If pattern space contains no newline, start a normal new cycle as if the sed -i 's/hello/world/' file.txt36 command was issued. Otherwise, delete text in the pattern space up to the first newline, and restart cycle with the resultant pattern space, without reading a new line of input. sed -i 's/hello/world/' file.txt71 Add a newline to the pattern space, then append the next line of input to the pattern space. If there is no more input then sed -i 's/hello/world/' file.txt22 exits without processing any more commands. When -z is used, a zero byte (the ascii ‘NUL’ character) is added between the lines (instead of a new line). By default sed -i 's/hello/world/' file.txt22 does not terminate if there is no ’next’ input line. This is a GNU extension which can be disabled with --posix. See N command on the last line. sed -n '1p ; $p' one.txt two.txt three.txt57 Print out the portion of the pattern space up to the first newline. sed -n '1p ; $p' one.txt two.txt three.txt46 Replace the contents of the hold space with the contents of the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt47 Append a newline to the contents of the hold space, and then append the contents of the pattern space to that of the hold space. sed -n '1p ; $p' one.txt two.txt three.txt44 Replace the contents of the pattern space with the contents of the hold space. sed -n '1p ; $p' one.txt two.txt three.txt45 Append a newline to the contents of the pattern space, and then append the contents of the hold space to that of the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt75 Exchange the contents of the hold and pattern spaces. 3.6 Commands for sed -i 's/hello/world/' file.txt 22 gurusIn most cases, use of these commands indicates that you are probably better off programming in something like sed OPTIONS... [SCRIPT] [INPUTFILE...]41 or Perl. But occasionally one is committed to sticking with sed -i 's/hello/world/' file.txt22, and these commands can enable one to write quite convoluted scripts. sed -n '1p ; $p' one.txt two.txt three.txt81 [No addresses allowed.] Specify the location of label for branch commands. In all other respects, a no-op. sed -n '1p ; $p' one.txt two.txt three.txt34 Unconditionally branch to label. The label may be omitted, in which case the next cycle is started. sed -n '1p ; $p' one.txt two.txt three.txt66 Branch to label only if there has been a successful sed -n '1p ; $p' one.txt two.txt three.txt67ubstitution since the last input line was read or conditional branch was taken. The label may be omitted, in which case the next cycle is started. 3.7 Commands Specific to GNU sed -i 's/hello/world/' file.txt 22These commands are specific to GNU sed -i 's/hello/world/' file.txt22, so you must use them with care and only when you are sure that hindering portability is not evil. They allow you to check for GNU sed -i 's/hello/world/' file.txt22 extensions or to do tasks that are required quite often, yet are unsupported by standard sed -i 's/hello/world/' file.txt22s. sed OPTIONS... [SCRIPT] [INPUTFILE...]51 This command allows one to pipe input from a shell command into pattern space. Without parameters, the sed -n '1p ; $p' one.txt two.txt three.txt41 command executes the command that is found in pattern space and replaces the pattern space with the output; a trailing newline is suppressed. If a parameter is specified, instead, the sed -n '1p ; $p' one.txt two.txt three.txt41 command interprets it as a command and sends its output to the output stream. The command can run across multiple lines, all but the last ending with a back-slash. In both cases, the results are undefined if the command to be executed contains a NUL character. Note that, unlike the sed OPTIONS... [SCRIPT] [INPUTFILE...]54 command, the output of the command will be printed immediately; the sed OPTIONS... [SCRIPT] [INPUTFILE...]54 command instead delays the output to the end of the current cycle. sed -n '1p ; $p' one.txt two.txt three.txt43 Print out the file name of the current input file (with a trailing newline). sed OPTIONS... [SCRIPT] [INPUTFILE...]57 This command accepts only one address. This command is the same as sed -n '1p ; $p' one.txt two.txt three.txt00, but will not print the contents of pattern space. Like sed -n '1p ; $p' one.txt two.txt three.txt00, it provides the ability to return an exit code to the caller. This command can be useful because the only alternative ways to accomplish this apparently trivial function are to use the -n option (which can unnecessarily complicate your script) or resorting to the following snippet, which wastes time by reading the whole file without any visible effect: sed -n '1p ; $p' one.txt two.txt three.txt0 sed -n '1p ; $p' one.txt two.txt three.txt64 Queue a line of filename to be read and inserted into the output stream at the end of the current cycle, or when the next input line is read. Note that if filename cannot be read, or if its end is reached, no line is appended, without any error indication. As with the sed OPTIONS... [SCRIPT] [INPUTFILE...]54 command, the special value /dev/stdin is supported for the file name, which reads a line from the standard input. sed -n '1p ; $p' one.txt two.txt three.txt68 Branch to label only if there have been no successful sed -n '1p ; $p' one.txt two.txt three.txt67ubstitutions since the last input line was read or conditional branch was taken. The label may be omitted, in which case the next cycle is started. sed OPTIONS... [SCRIPT] [INPUTFILE...]64 This command does nothing, but makes sed -i 's/hello/world/' file.txt22 fail if GNU sed -i 's/hello/world/' file.txt22 extensions are not supported, simply because other versions of sed -i 's/hello/world/' file.txt22 do not implement it. In addition, you can specify the version of sed -i 's/hello/world/' file.txt22 that your script requires, such as sed OPTIONS... [SCRIPT] [INPUTFILE...]69. The default is sed OPTIONS... [SCRIPT] [INPUTFILE...]70 because that is the first version that implemented this command. This command enables all GNU extensions even if sed -i 's/hello/world/' file.txt72 is set in the environment. sed -n '1p ; $p' one.txt two.txt three.txt74 Write to the given filename the portion of the pattern space up to the first newline. Everything said under the sed OPTIONS... [SCRIPT] [INPUTFILE...]26 command about file handling holds here too. sed -n '1p ; $p' one.txt two.txt three.txt77 This command empties the content of pattern space. It is usually the same as ‘s/.*//’, but is more efficient and works in the presence of invalid multibyte sequences in the input stream. POSIX mandates that such sequences are not matched by ‘.’, so that there is no portable way to clear sed -i 's/hello/world/' file.txt22’s buffers in the middle of the script in most multibyte locales (including UTF-8 locales). 3.8 Multiple commands syntaxThere are several methods to specify multiple commands in a sed -i 's/hello/world/' file.txt22 program. Using newlines is most natural when running a sed script from a file (using the -f option). On the command line, all sed -i 's/hello/world/' file.txt22 commands may be separated by newlines. Alternatively, you may specify each command as an argument to an -e option: sed -n '1p ; $p' one.txt two.txt three.txt1 A semicolon (‘;’) may be used to separate most simple commands: sed -n '1p ; $p' one.txt two.txt three.txt2 The sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt78, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt79, sed -n '1p ; $p' one.txt two.txt three.txt82, sed -n '1p ; $p' one.txt two.txt three.txt83, sed -n '1p ; $p' one.txt two.txt three.txt84, sed OPTIONS... [SCRIPT] [INPUTFILE...]83 commands can be separated with a semicolon (this is a non-portable GNU sed -i 's/hello/world/' file.txt22 extension). sed -n '1p ; $p' one.txt two.txt three.txt3 Labels used in sed -n '1p ; $p' one.txt two.txt three.txt82, sed -n '1p ; $p' one.txt two.txt three.txt83, sed -n '1p ; $p' one.txt two.txt three.txt84, sed OPTIONS... [SCRIPT] [INPUTFILE...]83 commands are read until a semicolon. Leading and trailing whitespace is ignored. In the examples below the label is ‘x’. The first example works with GNU sed -i 's/hello/world/' file.txt22. The second is a portable equivalent. For more information about branching and labels see Branching and flow control. sed -n '1p ; $p' one.txt two.txt three.txt4 3.8.1 Commands Requiring a newlineThe following commands cannot be separated by a semicolon and require a newline: sed -n '1p ; $p' one.txt two.txt three.txt26, sed -n '1p ; $p' one.txt two.txt three.txt27, sed -n '1p ; $p' one.txt two.txt three.txt28 (append/change/insert) All characters following sed -n '1p ; $p' one.txt two.txt three.txt26, sed -n '1p ; $p' one.txt two.txt three.txt27, sed -n '1p ; $p' one.txt two.txt three.txt28 commands are taken as the text to append/change/insert. Using a semicolon leads to undesirable results: sed -n '1p ; $p' one.txt two.txt three.txt5 Separate the commands using -e or a newline: sed -n '1p ; $p' one.txt two.txt three.txt6 Note that specifying the text to add (‘Hello’) immediately after sed -n '1p ; $p' one.txt two.txt three.txt26, sed -n '1p ; $p' one.txt two.txt three.txt27, sed -n '1p ; $p' one.txt two.txt three.txt28 is itself a GNU sed -i 's/hello/world/' file.txt22 extension. A portable, POSIX-compliant alternative is: sed -n '1p ; $p' one.txt two.txt three.txt7 sed -n '1p ; $p' one.txt two.txt three.txt78 (comment) All characters following ‘#’ until the next newline are ignored. sed -n '1p ; $p' one.txt two.txt three.txt8 sed OPTIONS... [SCRIPT] [INPUTFILE...]54, sed -i 's/hello/world/' file.txt88, sed OPTIONS... [SCRIPT] [INPUTFILE...]26, sed -i 's/hello/world/' file.txt33 (reading and writing files) The sed OPTIONS... [SCRIPT] [INPUTFILE...]54, sed -i 's/hello/world/' file.txt88, sed OPTIONS... [SCRIPT] [INPUTFILE...]26, sed -i 's/hello/world/' file.txt33 commands parse the filename until end of the line. If whitespace, comments or semicolons are found, they will be included in the filename, leading to unexpected results: sed -n '1p ; $p' one.txt two.txt three.txt9 Note that sed -i 's/hello/world/' file.txt22 silently ignores read/write errors in sed OPTIONS... [SCRIPT] [INPUTFILE...]54, sed -i 's/hello/world/' file.txt88, sed OPTIONS... [SCRIPT] [INPUTFILE...]26, sed -i 's/hello/world/' file.txt33 commands (such as missing files). In the following example, sed -i 's/hello/world/' file.txt22 tries to read a file named ‘hello.txt ; N’. The file is missing, and the error is silently ignored: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt0 sed -n '1p ; $p' one.txt two.txt three.txt41 (command execution) Any characters following the sed -n '1p ; $p' one.txt two.txt three.txt41 command until the end of the line will be sent to the shell. If whitespace, comments or semicolons are found, they will be included in the shell command, leading to unexpected results: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt1 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 317 (substitute with sed -n '1p ; $p' one.txt two.txt three.txt41 or sed OPTIONS... [SCRIPT] [INPUTFILE...]26 flags) In a substitution command, the sed OPTIONS... [SCRIPT] [INPUTFILE...]26 flag writes the substitution result to a file, and the sed -n '1p ; $p' one.txt two.txt three.txt41 flag executes the subsitution result as a shell command. As with the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 322 commands, these must be terminated with a newline. If whitespace, comments or semicolons are found, they will be included in the shell command or filename, leading to unexpected results: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt2 4 Addresses: selecting lines4.1 Addresses overviewAddresses determine on which line(s) the sed -i 's/hello/world/' file.txt22 command will be executed. The following command replaces the word ‘hello’ with ‘world’ only on line 144: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt3 If no addresses are given, the command is performed on all lines. The following command replaces the word ‘hello’ with ‘world’ on all lines in the input file: sed 's/hello/world/' input.txt > output.txt Addresses can contain regular expressions to match lines based on content instead of line numbers. The following command replaces the word ‘hello’ with ‘world’ only in lines containing the word ‘apple’: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt5 An address range is specified with two addresses separated by a comma ( $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 324). Addresses can be numeric, regular expressions, or a mix of both. The following command replaces the word ‘hello’ with ‘world’ only in lines 4 to 17 (inclusive): sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt6 Appending the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 325 character to the end of an address specification (before the command letter) negates the sense of the match. That is, if the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 325 character follows an address or an address range, then only lines which do not match the addresses will be selected. The following command replaces the word ‘hello’ with ‘world’ only in lines not containing the word ‘apple’: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt7 The following command replaces the word ‘hello’ with ‘world’ only in lines 1 to 3 and 18 till the last line of the input file (i.e. excluding lines 4 to 17): sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt8 4.2 Selecting lines by numbersAddresses in a sed -i 's/hello/world/' file.txt22 script can be in any of the following forms: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt28 Specifying a line number will match only that line in the input. (Note that sed -i 's/hello/world/' file.txt22 counts lines continuously across all input files unless -i or -s options are specified.) sed -i 's/hello/world/' file.txt87 This address matches the last line of the last file of input, or the last line of each file when the -i or -s options are specified. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 331 This GNU extension matches every stepth line starting with line first. In particular, lines will be selected when there exists a non-negative n such that the current line-number equals first + (n * step). Thus, one would use $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 332 to select the odd-numbered lines and $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 333 for even-numbered lines; to pick every third line starting with the second, ‘2~3’ would be used; to pick every fifth line starting with the tenth, use ‘10~5’; and ‘50~0’ is just an obscure way of saying $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 334. The following commands demonstrate the step address usage: sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt9 4.3 selecting lines by text matchingGNU sed -i 's/hello/world/' file.txt22 supports the following regular expression addresses. The default regular expression is Basic Regular Expression (BRE). If -E or -r options are used, The regular expression should be in Extended Regular Expression (ERE) syntax. See BRE vs ERE. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 336 This will select any line which matches the regular expression regexp. If regexp itself includes any sed -n '1p ; $p' one.txt two.txt three.txt94 characters, each must be escaped by a backslash ( sed -n '1p ; $p' one.txt two.txt three.txt97). The following command prints lines in /etc/passwd which end with ‘bash’5: sed OPTIONS... [SCRIPT] [INPUTFILE...]0 The empty regular expression ‘//’ repeats the last regular expression match (the same holds if the empty regular expression is passed to the sed -n '1p ; $p' one.txt two.txt three.txt67 command). Note that modifiers to regular expressions are evaluated when the regular expression is compiled, thus it is invalid to specify them together with the empty regular expression. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 340 (The $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 341 may be replaced by any other single character.) This also matches the regular expression regexp, but allows one to use a different delimiter than sed -n '1p ; $p' one.txt two.txt three.txt94. This is particularly useful if the regexp itself contains a lot of slashes, since it avoids the tedious escaping of every sed -n '1p ; $p' one.txt two.txt three.txt94. If regexp itself includes any delimiter characters, each must be escaped by a backslash ( sed -n '1p ; $p' one.txt two.txt three.txt97). The following commands are equivalent. They print lines which start with ‘/home/alice/documents/’: sed OPTIONS... [SCRIPT] [INPUTFILE...]1 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 345 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 346 The sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt45 modifier to regular-expression matching is a GNU extension which causes the regexp to be matched in a case-insensitive manner. In many other programming languages, a lower case sed -n '1p ; $p' one.txt two.txt three.txt28 is used for case-insensitive regular expression matching. However, in sed -i 's/hello/world/' file.txt22 the sed -n '1p ; $p' one.txt two.txt three.txt28 is used for the insert command (see insert command). Observe the difference between the following examples. In this example, $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 351 is the address: regular expression with sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt45 modifier. sed -i 's/hello/world/' file.txt36 is the delete command: sed OPTIONS... [SCRIPT] [INPUTFILE...]2 Here, $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 354 is the address: a regular expression. sed -n '1p ; $p' one.txt two.txt three.txt28 is the insert command. sed -i 's/hello/world/' file.txt36 is the value to insert. A line with ‘d’ is then inserted above the matched line: sed OPTIONS... [SCRIPT] [INPUTFILE...]3 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 357 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 358 The sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt49 modifier to regular-expression matching is a GNU sed -i 's/hello/world/' file.txt22 extension which directs GNU sed -i 's/hello/world/' file.txt22 to match the regular expression in multi-line mode. The modifier causes sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 and sed -i 's/hello/world/' file.txt87 to match respectively (in addition to the normal behavior) the empty string after a newline, and the empty string before a newline. There are special character sequences ( sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt56 and sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt57) which always match the beginning or the end of the buffer. In addition, the period character does not match a new-line character in multi-line mode. Regex addresses operate on the content of the current pattern space. If the pattern space is changed (for example with $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 366 command) the regular expression matching will operate on the changed text. In the following example, automatic printing is disabled with -n. The $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 367 command changes lines containing ‘2’ to ‘X’. The command $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 368 matches lines with digits and prints them. Because the second line is changed before the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 369 regex, it will not match and will not be printed: sed OPTIONS... [SCRIPT] [INPUTFILE...]4 4.4 Range AddressesAn address range can be specified by specifying two addresses separated by a comma ( $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 324). An address range matches lines starting from where the first address matches, and continues until the second address matches (inclusively): sed OPTIONS... [SCRIPT] [INPUTFILE...]5 If the second address is a regexp, then checking for the ending match will start with the line following the line which matched the first address: a range will always span at least two lines (except of course if the input stream ends). sed OPTIONS... [SCRIPT] [INPUTFILE...]6 If the second address is a number less than (or equal to) the line matching the first address, then only the one line is matched: sed OPTIONS... [SCRIPT] [INPUTFILE...]7 GNU sed -i 's/hello/world/' file.txt22 also supports some special two-address forms; all these are GNU extensions: $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 372 A line number of $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 373 can be used in an address specification like $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 372 so that sed -i 's/hello/world/' file.txt22 will try to match regexp in the first input line too. In other words, $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 372 is similar to $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 377, except that if addr2 matches the very first line of input the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 372 form will consider it to end the range, whereas the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 377 form will match the beginning of its range and hence make the range span up to the second occurrence of the regular expression. Note that this is the only place where the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 373 address makes sense; there is no 0-th line and commands which are given the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 373 address in any other way will give an error. The following examples demonstrate the difference between starting with address 1 and 0: sed OPTIONS... [SCRIPT] [INPUTFILE...]8 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 382 Matches addr1 and the N lines following addr1. sed OPTIONS... [SCRIPT] [INPUTFILE...]9 addr1 can be a line number or a regular expression. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 383 Matches addr1 and the lines following addr1 until the next line whose input line number is a multiple of N. The following command prints starting at line 6, until the next line which is a multiple of 4 (i.e. line 8): $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 30 addr1 can be a line number or a regular expression. 5 Regular Expressions: selecting text5.1 Overview of regular expression in sed -i 's/hello/world/' file.txt 22To know how to use sed -i 's/hello/world/' file.txt22, people should understand regular expressions (regexp for short). A regular expression is a pattern that is matched against a subject string from left to right. Most characters are ordinary: they stand for themselves in a pattern, and match the corresponding characters. Regular expressions in sed -i 's/hello/world/' file.txt22 are specified between two slashes. The following command prints lines containing the word ‘hello’: The above example is equivalent to this $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 387 command: The power of regular expressions comes from the ability to include alternatives and repetitions in the pattern. These are encoded in the pattern by the use of special characters, which do not stand for themselves but instead are interpreted in some special way. The character sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 (caret) in a regular expression matches the beginning of the line. The character $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 389 (dot) matches any single character. The following sed -i 's/hello/world/' file.txt22 command matches and prints lines which start with the letter ‘b’, followed by any single character, followed by the letter ‘d’: $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 31 The following sections explain the meaning and usage of special characters in regular expressions. 5.2 Basic (BRE) and extended (ERE) regular expressionBasic and extended regular expressions are two variations on the syntax of the specified pattern. Basic Regular Expression (BRE) syntax is the default in sed -i 's/hello/world/' file.txt22 (and similarly in $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 387). Use the POSIX-specified -E option (-r, --regexp-extended) to enable Extended Regular Expression (ERE) syntax. In GNU sed -i 's/hello/world/' file.txt22, the only difference between basic and extended regular expressions is in the behavior of a few special characters: ‘?’, ‘+’, parentheses, braces (‘{}’), and ‘|’. With basic (BRE) syntax, these characters do not have special meaning unless prefixed with a backslash (‘\’); While with extended (ERE) syntax it is reversed: these characters are special unless they are prefixed with backslash (‘\’). Desired patternBasic (BRE) SyntaxExtended (ERE) Syntaxliteral ‘+’ (plus sign)$ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 32 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 33One or more ‘a’ characters followed by ‘b’ (plus sign as special meta-character) $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 34 $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 35 5.3 Overview of basic regular expression syntaxHere is a brief description of regular expression syntax as used in sed -i 's/hello/world/' file.txt22. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 395 A single ordinary character matches itself. sed -i 's/hello/world/' file.txt60 Matches a sequence of zero or more instances of matches for the preceding regular expression, which must be an ordinary character, a special character preceded by sed -n '1p ; $p' one.txt two.txt three.txt97, a $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 389, a grouped regexp (see below), or a bracket expression. As a GNU extension, a postfixed regular expression can also be followed by sed -i 's/hello/world/' file.txt60; for example, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE00 is equivalent to # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE01. POSIX 1003.1-2001 says that sed -i 's/hello/world/' file.txt60 stands for itself when it appears at the start of a regular expression or subexpression, but many nonGNU implementations do not support this and portable scripts should instead use # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE03 in these contexts. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 389 Matches any character, including newline. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 Matches the null string at beginning of the pattern space, i.e. what appears after the circumflex must appear at the beginning of the pattern space. In most scripts, pattern space is initialized to the content of each line (see How sed -i 's/hello/world/' file.txt22 works). So, it is a useful simplification to think of # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE07 as matching only lines where ‘#include’ is the first thing on line—if there are spaces before, for example, the match fails. This simplification is valid as long as the original content of pattern space is not modified, for example with an sed -n '1p ; $p' one.txt two.txt three.txt67 command. sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 acts as a special character only at the beginning of the regular expression or subexpression (that is, after sed -n '1p ; $p' one.txt two.txt three.txt91 or # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE11). Portable scripts should avoid sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 at the beginning of a subexpression, though, as POSIX allows implementations that treat sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 as an ordinary character in that context. sed -i 's/hello/world/' file.txt87 It is the same as sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54, but refers to end of pattern space. sed -i 's/hello/world/' file.txt87 also acts as a special character only at the end of the regular expression or subexpression (that is, before sed -n '1p ; $p' one.txt two.txt three.txt92 or # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE11), and its use at the end of a subexpression is not portable. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE19 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE20 Matches any single character in list: for example, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE21 matches all vowels. A list may include sequences like # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE22, which matches any character between (inclusive) char1 and char2. See Character Classes and Bracket Expressions. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE23 As sed -i 's/hello/world/' file.txt60, but matches one or more. It is a GNU extension. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE25 As sed -i 's/hello/world/' file.txt60, but only matches zero or one. It is a GNU extension. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE27 As sed -i 's/hello/world/' file.txt60, but matches exactly i sequences (i is a decimal integer; for portability, keep it between 0 and 255 inclusive). # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE29 Matches between i and j, inclusive, sequences. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE30 Matches more than or equal to i sequences. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE31 Groups the inner regexp as a whole, this is used to:
# WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE35 Matches either regexp1 or regexp2. Use parentheses to use complex alternative regular expressions. The matching process tries each alternative in turn, from left to right, and the first one that succeeds is used. It is a GNU extension. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE36 Matches the concatenation of regexp1 and regexp2. Concatenation binds more tightly than # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE11, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54, and sed -i 's/hello/world/' file.txt87, but less tightly than the other regular expression operators. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE40 Matches the digit-th # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE41 parenthesized subexpression in the regular expression. This is called a back reference. Subexpressions are implicitly numbered by counting occurrences of sed -n '1p ; $p' one.txt two.txt three.txt91 left-to-right. sed -n '1p ; $p' one.txt two.txt three.txt90 Matches the newline character. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE44 Matches char, where char is one of sed -i 's/hello/world/' file.txt87, sed -i 's/hello/world/' file.txt60, $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 389, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE48, sed -n '1p ; $p' one.txt two.txt three.txt97, or sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54. Note that the only C-like backslash sequences that you can portably assume to be interpreted are sed -n '1p ; $p' one.txt two.txt three.txt90 and sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt95; in particular # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE53 is not portable, and matches a ‘t’ under most implementations of sed -i 's/hello/world/' file.txt22, rather than a tab character. Note that the regular expression matcher is greedy, i.e., matches are attempted from left to right and, if two or more matches are possible starting at the same character, it selects the longest. Examples: ‘abcdef’Matches ‘abcdef’. ‘a*b’Matches zero or more ‘a’s followed by a single ‘b’. For example, ‘b’ or ‘aaaaab’. ‘a\?b’Matches ‘b’ or ‘ab’. ‘a\+b\+’Matches one or more ‘a’s followed by one or more ‘b’s: ‘ab’ is the shortest possible match, but other examples are ‘aaaab’ or ‘abbbbb’ or ‘aaaaaabbbbbbb’. ‘.*’‘.\+’These two both match all the characters in a string; however, the first matches every string (including the empty string), while the second matches only strings containing at least one character. ‘^main.*(.*)’This matches a string starting with ‘main’, followed by an opening and closing parenthesis. The ‘n’, ‘(’ and ‘)’ need not be adjacent. ‘^#’This matches a string beginning with ‘#’. ‘\\$’This matches a string ending with a single backslash. The regexp contains two backslashes for escaping. ‘\$’Instead, this matches a string consisting of a single dollar sign, because it is escaped. ‘[a-zA-Z0-9]’In the C locale, this matches any ASCII letters or digits. ‘[^ TAB]\+’(Here TAB stands for a single tab character.) This matches a string of one or more characters, none of which is a space or a tab. Usually this means a word. ‘^\(.*\)\n\1$’This matches a string consisting of two equal substrings separated by a newline. ‘.\{9\}A$’This matches nine characters followed by an ‘A’ at the end of a line. ‘^.\{15\}A’This matches the start of a string that contains 16 characters, the last of which is an ‘A’. 5.4 Overview of extended regular expression syntaxThe only difference between basic and extended regular expressions is in the behavior of a few characters: ‘?’, ‘+’, parentheses, braces (‘{}’), and ‘|’. While basic regular expressions require these to be escaped if you want them to behave as special characters, when using extended regular expressions you must escape them if you want them to match a literal character. ‘|’ is special here because ‘\|’ is a GNU extension – standard basic regular expressions do not provide its functionality. Examples: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE55 becomes ‘abc\?’ when using extended regular expressions. It matches the literal string ‘abc?’. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE56 becomes ‘c+’ when using extended regular expressions. It matches one or more ‘c’s. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE57 becomes ‘a{3,}’ when using extended regular expressions. It matches three or more ‘a’s. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE58 becomes ‘(abc){2,3}’ when using extended regular expressions. It matches either ‘abcabc’ or ‘abcabcabc’. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE59 becomes ‘(abc*)\1’ when using extended regular expressions. Backreferences must still be escaped when using extended regular expressions. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE60 becomes ‘a|b’ when using extended regular expressions. It matches ‘a’ or ‘b’. 5.5 Character Classes and Bracket ExpressionsA bracket expression is a list of characters enclosed by ‘[’ and ‘]’. It matches any single character in that list; if the first character of the list is the caret ‘^’, then it matches any character not in the list. For example, the following command replaces the words ‘gray’ or ‘grey’ with ‘blue’: Bracket expressions can be used in both basic and extended regular expressions (that is, with or without the -E/-r options). Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive. In the default C locale, the sorting sequence is the native character order; for example, ‘[a-d]’ is equivalent to ‘[abcd]’. Finally, certain named classes of characters are predefined within bracket expressions, as follows. These named classes must be used inside brackets themselves. Correct usage: $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 36 Incorrect usage is rejected by newer sed -i 's/hello/world/' file.txt22 versions. Older versions accepted it but treated it as a single bracket expression (which is equivalent to ‘[dgit:]’, that is, only the characters d/g/i/t/:): $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 37‘[:alnum:]’ Alphanumeric characters: ‘[:alpha:]’ and ‘[:digit:]’; in the ‘C’ locale and ASCII character encoding, this is the same as ‘[0-9A-Za-z]’. ‘[:alpha:]’Alphabetic characters: ‘[:lower:]’ and ‘[:upper:]’; in the ‘C’ locale and ASCII character encoding, this is the same as ‘[A-Za-z]’. ‘[:blank:]’Blank characters: space and tab. ‘[:cntrl:]’Control characters. In ASCII, these characters have octal codes 000 through 037, and 177 (DEL). In other character sets, these are the equivalent characters, if any. ‘[:digit:]’Digits: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE62.‘[:graph:]’ Graphical characters: ‘[:alnum:]’ and ‘[:punct:]’. ‘[:lower:]’Lower-case letters; in the ‘C’ locale and ASCII character encoding, this is # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE63.‘[:print:]’ Printable characters: ‘[:alnum:]’, ‘[:punct:]’, and space. ‘[:punct:]’Punctuation characters; in the ‘C’ locale and ASCII character encoding, this is # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE64.‘[:space:]’ Space characters: in the ‘C’ locale, this is tab, newline, vertical tab, form feed, carriage return, and space. ‘[:upper:]’Upper-case letters: in the ‘C’ locale and ASCII character encoding, this is # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE65.‘[:xdigit:]’ Hexadecimal digits: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE66. Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression. Most meta-characters lose their special meaning inside bracket expressions: ‘]’ends the bracket expression if it’s not the first list item. So, if you want to make the ‘]’ character a list item, you must put it first. ‘-’represents the range if it’s not first or last in a list or the ending point of a range. ‘^’represents the characters not in the list. If you want to make the ‘^’ character a list item, place it anywhere but first. TODO: incorporate this paragraph (copied verbatim from BRE section). The characters sed -i 's/hello/world/' file.txt87, sed -i 's/hello/world/' file.txt60, $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 389, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE48, and sed -n '1p ; $p' one.txt two.txt three.txt97 are normally not special within list. For example, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE72 matches either ‘\’ or ‘*’, because the sed -n '1p ; $p' one.txt two.txt three.txt97 is not special here. However, strings like # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE74, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE75, and # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE76 are special within list and represent collating symbols, equivalence classes, and character classes, respectively, and # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE48 is therefore special within list when it is followed by $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 389, sed -n '1p ; $p' one.txt two.txt three.txt80, or sed OPTIONS... [SCRIPT] [INPUTFILE...]83. Also, when not in sed -i 's/hello/world/' file.txt72 mode, special escapes like sed -n '1p ; $p' one.txt two.txt three.txt90 and # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE53 are recognized within list. See Escapes.‘[.’ represents the open collating symbol. ‘.]’represents the close collating symbol. ‘[=’represents the open equivalence class. ‘=]’represents the close equivalence class. ‘[:’represents the open character class symbol, and should be followed by a valid character class name. ‘:]’represents the close character class symbol. 5.6 regular expression extensionsThe following sequences have special meaning inside regular expressions (used in addresses and the sed -n '1p ; $p' one.txt two.txt three.txt67 command). These can be used in both basic and extended regular expressions (that is, with or without the -E/-r options). # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE85 Matches any “word” character. A “word” character is any letter or digit or the underscore character. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 38 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE86 Matches any “non-word” character. $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 39 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE87 Matches a word boundary; that is it matches if the character to the left is a “word” character and the character to the right is a “non-word” character, or vice-versa. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE0 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE88 Matches everywhere but on a word boundary; that is it matches if the character to the left and the character to the right are either both “word” characters or both “non-word” characters. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE1 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE89 Matches whitespace characters (spaces and tabs). Newlines embedded in the pattern/hold spaces will also match: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE2 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE90 Matches non-whitespace characters. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE3 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE91 Matches the beginning of a word. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE4 # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE92 Matches the end of a word. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE5 sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt56 Matches only at the start of pattern space. This is different from sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt54 in multi-line mode. Compare the following two examples: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE6 sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt57 Matches only at the end of pattern space. This is different from sed -i 's/hello/world/' file.txt87 in multi-line mode. 5.7 Back-references and Subexpressionsback-references are regular expression commands which refer to a previous part of the matched regular expression. Back-references are specified with backslash and a single digit (e.g. ‘\1’). The part of the regular expression they refer to is called a subexpression, and is designated with parentheses. Back-references and subexpressions are used in two cases: in the regular expression search pattern, and in the replacement part of the sed -n '1p ; $p' one.txt two.txt three.txt67 command (see Regular Expression Addresses and The "s" Command). In a regular expression pattern, back-references are used to match the same content as a previously matched subexpression. In the following example, the subexpression is ‘.’ - any single character (being surrounded by parentheses makes it a subexpression). The back-reference ‘\1’ asks to match the same content (same character) as the sub-expression. The command below matches words starting with any character, followed by the letter ‘o’, followed by the same character as the first. # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE7 Multiple subexpressions are automatically numbered from left-to-right. This command searches for 6-letter palindromes (the first three letters are 3 subexpressions, followed by 3 back-references in reverse order): # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE8 In the sed -n '1p ; $p' one.txt two.txt three.txt67 command, back-references can be used in the replacement part to refer back to subexpressions in the regexp part. The following example uses two subexpressions in the regular expression to match two space-separated words. The back-references in the replacement part prints the words in a different order: # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE9 When used with alternation, if the group does not participate in the match then the back-reference makes the whole match fail. For example, ‘a(.)|b\1’ will not match ‘ba’. When multiple regular expressions are given with -e or from a file (‘-f file’), back-references are local to each expression. 5.8 Escape Sequences - specifying special charactersUntil this chapter, we have only encountered escapes of the form ‘\^’, which tell sed -i 's/hello/world/' file.txt22 not to interpret the circumflex as a special character, but rather to take it literally. For example, ‘\*’ matches a single asterisk rather than zero or more backslashes. This chapter introduces another kind of escape6—that is, escapes that are applied to a character or sequence of characters that ordinarily are taken literally, and that sed -i 's/hello/world/' file.txt22 replaces with a special character. This provides a way of encoding non-printable characters in patterns in a visible manner. There is no restriction on the appearance of non-printing characters in a sed -i 's/hello/world/' file.txt22 script but when a script is being prepared in the shell or by text editing, it is usually easier to use one of the following escape sequences than the binary character it represents: The list of these escapes is: $ echo | sed 'Q42' ; echo $? 4202 Produces or matches a BEL character, that is an “alert” (ASCII 7). $ echo | sed 'Q42' ; echo $? 4203 Produces or matches a form feed (ASCII 12). sed -n '1p ; $p' one.txt two.txt three.txt90 Produces or matches a newline (ASCII 10). $ echo | sed 'Q42' ; echo $? 4205 Produces or matches a carriage return (ASCII 13). # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE53 Produces or matches a horizontal tab (ASCII 9). $ echo | sed 'Q42' ; echo $? 4207 Produces or matches a so called “vertical tab” (ASCII 11). $ echo | sed 'Q42' ; echo $? 4208 Produces or matches CONTROL-x, where x is any character. The precise effect of ‘\cx’ is as follows: if x is a lower case letter, it is converted to upper case. Then bit 6 of the character (hex 40) is inverted. Thus ‘\cz’ becomes hex 1A, but ‘\c{’ becomes hex 3B, while ‘\c;’ becomes hex 7B. $ echo | sed 'Q42' ; echo $? 4209 Produces or matches a character whose decimal ASCII value is xxx. $ echo | sed 'Q42' ; echo $? 4210 Produces or matches a character whose octal ASCII value is xxx. $ echo | sed 'Q42' ; echo $? 4211 Produces or matches a character whose hexadecimal ASCII value is xx. ‘\b’ (backspace) was omitted because of the conflict with the existing “word boundary” meaning. 5.8.1 Escaping PrecedenceGNU sed -i 's/hello/world/' file.txt22 processes escape sequences before passing the text onto the regular-expression matching of the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 366 command and Address matching. Thus the follwing two commands are equivalent (‘0x5e’ is the hexadecimal ASCII value of the character ‘^’): $ echo | sed 'Q42' ; echo $? 420 As are the following (‘0x5b’,‘0x5d’ are the hexadecimal ASCII values of ‘[’,‘]’, respectively): $ echo | sed 'Q42' ; echo $? 421 However it is recommended to avoid such special characters due to unexpected edge-cases. For example, the following are not equivalent: $ echo | sed 'Q42' ; echo $? 422 5.9 Multibyte characters and Locale ConsiderationsGNU sed -i 's/hello/world/' file.txt22 processes valid multibyte characters in multibyte locales (e.g. $ echo | sed 'Q42' ; echo $? 4215). 7 The following example uses the Greek letter Capital Sigma (Σ, Unicode code point $ echo | sed 'Q42' ; echo $? 4216). In a $ echo | sed 'Q42' ; echo $? 4215 locale, sed -i 's/hello/world/' file.txt22 correctly processes the Sigma as one character despite it being 2 octets (bytes): $ echo | sed 'Q42' ; echo $? 423 To force sed -i 's/hello/world/' file.txt22 to process octets separately, use the $ echo | sed 'Q42' ; echo $? 4220 locale (also known as the $ echo | sed 'Q42' ; echo $? 4221 locale): $ echo | sed 'Q42' ; echo $? 424 5.9.1 Invalid multibyte characterssed -i 's/hello/world/' file.txt22’s regular expressions do not match invalid multibyte sequences in a multibyte locale. In the following examples, the ascii value $ echo | sed 'Q42' ; echo $? 4223 is an incomplete multibyte character (shown here as �). The regular expression ‘.’ does not match it: $ echo | sed 'Q42' ; echo $? 425 Similarly, the ’catch-all’ regular expression ‘.*’ does not match the entire line: $ echo | sed 'Q42' ; echo $? 426 GNU sed -i 's/hello/world/' file.txt22 offers the special sed -n '1p ; $p' one.txt two.txt three.txt77 command to clear the current pattern space regardless of invalid multibyte characters (i.e. it works like $ echo | sed 'Q42' ; echo $? 4226 but also removes invalid multibyte characters): $ echo | sed 'Q42' ; echo $? 427 Alternatively, force the $ echo | sed 'Q42' ; echo $? 4220 locale to process each octet separately (every octet is a valid character in the $ echo | sed 'Q42' ; echo $? 4220 locale): $ echo | sed 'Q42' ; echo $? 428 sed -i 's/hello/world/' file.txt22’s inability to process invalid multibyte characters can be used to detect such invalid sequences in a file. In the following examples, the $ echo | sed 'Q42' ; echo $? 4230 is an invalid multibyte sequence, while $ echo | sed 'Q42' ; echo $? 4231 is a valid multibyte sequence (of the Greek Sigma character). The following sed -i 's/hello/world/' file.txt22 program removes all valid characters using $ echo | sed 'Q42' ; echo $? 4233. Any content left in the pattern space (the invalid characters) are added to the hold space using the sed -n '1p ; $p' one.txt two.txt three.txt47 command. On the last line ( sed -i 's/hello/world/' file.txt87), the hold space is retrieved ( sed -n '1p ; $p' one.txt two.txt three.txt75), newlines are removed ( $ echo | sed 'Q42' ; echo $? 4237), and any remaining octets are printed unambiguously ( sed -i 's/hello/world/' file.txt67). Thus, any invalid multibyte sequences are printed as octal values: $ echo | sed 'Q42' ; echo $? 429 With a few more commands, sed -i 's/hello/world/' file.txt22 can print the exact line number corresponding to each invalid characters (line 3). These characters can then be removed by forcing the $ echo | sed 'Q42' ; echo $? 4220 locale and using octal escape sequences: sed '30,35d' input.txt > output.txt0 5.9.2 Upper/Lower case conversionGNU sed -i 's/hello/world/' file.txt22’s substitute command ( sed -n '1p ; $p' one.txt two.txt three.txt67) supports upper/lower case conversions using sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt05, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt04 codes. These conversions support multibyte characters: sed '30,35d' input.txt > output.txt1 See The "s" Command. 5.9.3 Multibyte regexp character classesIn other locales, the sorting sequence is not specified, and ‘[a-d]’ might be equivalent to ‘[abcd]’ or to ‘[aBbCcDd]’, or it might fail to match any character, or the set of characters that it matches might even be erratic. To obtain the traditional interpretation of bracket expressions, you can use the ‘C’ locale by setting the $ echo | sed 'Q42' ; echo $? 4245 environment variable to the value ‘C’. sed '30,35d' input.txt > output.txt2 Their interpretation depends on the $ echo | sed 'Q42' ; echo $? 4246 locale; for example, ‘[[:alnum:]]’ means the character class of numbers and letters in the current locale. TODO: show example of collation sed '30,35d' input.txt > output.txt3 6 Advanced sed -i 's/hello/world/' file.txt 22: cycles and buffers6.1 How sed -i 's/hello/world/' file.txt 22 Workssed -i 's/hello/world/' file.txt22 maintains two data buffers: the active pattern space, and the auxiliary hold space. Both are initially empty. sed -i 's/hello/world/' file.txt22 operates by performing the following cycle on each line of input: first, sed -i 's/hello/world/' file.txt22 reads one line from the input stream, removes any trailing newline, and places it in the pattern space. Then commands are executed; each command can have an address associated to it: addresses are a kind of condition code, and a command is only executed if the condition is verified before the command is to be executed. When the end of the script is reached, unless the -n option is in use, the contents of pattern space are printed out to the output stream, adding back the trailing newline if it was removed.8 Then the next cycle starts for the next input line. Unless special commands (like ‘D’) are used, the pattern space is deleted between two cycles. The hold space, on the other hand, keeps its data between cycles (see commands ‘h’, ‘H’, ‘x’, ‘g’, ‘G’ to move data between both buffers). 6.2 Hold and Pattern BuffersTODO 6.3 Multiline techniques - using D,G,H,N,P to process multiple linesMultiple lines can be processed as one buffer using the sed -n '1p ; $p' one.txt two.txt three.txt39, sed -n '1p ; $p' one.txt two.txt three.txt45, sed -n '1p ; $p' one.txt two.txt three.txt47, sed -i 's/hello/world/' file.txt71, sed -n '1p ; $p' one.txt two.txt three.txt57. They are similar to their lowercase counterparts ( sed -i 's/hello/world/' file.txt36, sed -n '1p ; $p' one.txt two.txt three.txt44, sed -n '1p ; $p' one.txt two.txt three.txt46, sed -n '1p ; $p' one.txt two.txt three.txt52, sed -i 's/hello/world/' file.txt37), except that these commands append or subtract data while respecting embedded newlines - allowing adding and removing lines from the pattern and hold spaces. They operate as follows: sed -n '1p ; $p' one.txt two.txt three.txt39 deletes line from the pattern space until the first newline, and restarts the cycle. sed -n '1p ; $p' one.txt two.txt three.txt45 appends line from the hold space to the pattern space, with a newline before it. sed -n '1p ; $p' one.txt two.txt three.txt47 appends line from the pattern space to the hold space, with a newline before it. sed -i 's/hello/world/' file.txt71 appends line from the input file to the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt57 prints line from the pattern space until the first newline. The following example illustrates the operation of sed -i 's/hello/world/' file.txt71 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands: sed '30,35d' input.txt > output.txt4
A common technique to process blocks of text such as paragraphs (instead of line-by-line) is using the following construct: sed '30,35d' input.txt > output.txt5
The following example demonstrates this technique: sed '30,35d' input.txt > output.txt6 For more annotated examples, see Text search across multiple lines and Line length adjustment. 6.4 Branching and Flow ControlThe branching commands sed -n '1p ; $p' one.txt two.txt three.txt82, sed -n '1p ; $p' one.txt two.txt three.txt83, and sed -n '1p ; $p' one.txt two.txt three.txt84 enable changing the flow of sed -i 's/hello/world/' file.txt22 programs. By default, sed -i 's/hello/world/' file.txt22 reads an input line into the pattern buffer, then continues to processes all commands in order. Commands without addresses affect all lines. Commands with addresses affect only matching lines. See Execution Cycle and Addresses overview. sed -i 's/hello/world/' file.txt22 does not support a typical $ echo | sed 'Q42' ; echo $? 4285 construct. Instead, some commands can be used as conditionals or to change the default flow control: sed -i 's/hello/world/' file.txt36 delete (clears) the current pattern space, and restart the program cycle without processing the rest of the commands and without printing the pattern space. sed -n '1p ; $p' one.txt two.txt three.txt39 delete the contents of the pattern space up to the first newline, and restart the program cycle without processing the rest of the commands and without printing the pattern space. $ echo | sed 'Q42' ; echo $? 4288 $ echo | sed 'Q42' ; echo $? 4289 $ echo | sed 'Q42' ; echo $? 4290 $ echo | sed 'Q42' ; echo $? 4291 Addresses and regular expressions can be used as an $ echo | sed 'Q42' ; echo $? 4285 conditional: If [addr] matches the current pattern space, execute the command(s). For example: The command $ echo | sed 'Q42' ; echo $? 4293 means: if the current pattern matches the regular expression $ echo | sed 'Q42' ; echo $? 4294 (a line starting with a hash), then execute the sed -i 's/hello/world/' file.txt36 command: delete the line without printing it, and restart the program cycle immediately. sed -n '1p ; $p' one.txt two.txt three.txt82 branch unconditionally (that is: always jump to a label, skipping or repeating other commands, without restarting a new cycle). Combined with an address, the branch can be conditionally executed on matched lines. sed -n '1p ; $p' one.txt two.txt three.txt83 branch conditionally (that is: jump to a label) only if a $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 366 command has succeeded since the last input line was read or another conditional branch was taken. sed -n '1p ; $p' one.txt two.txt three.txt84 similar but opposite to the sed -n '1p ; $p' one.txt two.txt three.txt83 command: branch only if there has been no successful substitutions since the last input line was read. The following two sed -i 's/hello/world/' file.txt22 programs are equivalent. The first (contrived) example uses the sed -n '1p ; $p' one.txt two.txt three.txt82 command to skip the $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 366 command on lines containing ‘1’. The second example uses an address with negation (‘!’) to perform substitution only on desired lines. The sed '30,35d' input.txt > output.txt04 command is still executed on all lines: sed '30,35d' input.txt > output.txt7 6.4.1 Branching and CyclesThe sed -n '1p ; $p' one.txt two.txt three.txt82, sed -n '1p ; $p' one.txt two.txt three.txt83 and sed -n '1p ; $p' one.txt two.txt three.txt84 commands can be followed by a label (typically a single letter). Labels are defined with a colon followed by one or more letters (e.g. ‘:x’). If the label is omitted the branch commands restart the cycle. Note the difference between branching to a label and restarting the cycle: when a cycle is restarted, sed -i 's/hello/world/' file.txt22 first prints the current content of the pattern space, then reads the next input line into the pattern space; Jumping to a label (even if it is at the beginning of the program) does not print the pattern space and does not read the next input line. The following program is a no-op. The sed -n '1p ; $p' one.txt two.txt three.txt82 command (the only command in the program) does not have a label, and thus simply restarts the cycle. On each cycle, the pattern space is printed and the next input line is read: The following example is an infinite-loop - it doesn’t terminate and doesn’t print anything. The sed -n '1p ; $p' one.txt two.txt three.txt82 command jumps to the ‘x’ label, and a new cycle is never started: sed '30,35d' input.txt > output.txt8 Branching is often complemented with the sed -n '1p ; $p' one.txt two.txt three.txt52 or sed -i 's/hello/world/' file.txt71 commands: both commands read the next input line into the pattern space without waiting for the cycle to restart. Before reading the next input line, sed -n '1p ; $p' one.txt two.txt three.txt52 prints the current pattern space then empties it, while sed -i 's/hello/world/' file.txt71 appends a newline and the next input line to the pattern space. Consider the following two examples: sed '30,35d' input.txt > output.txt9
6.4.2 Branching example: joining linesAs a real-world example of using branching, consider the case of quoted-printable files, typically used to encode email messages. In these files long lines are split and marked with a soft line break consisting of a single ‘=’ character at the end of the line: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt01 The following program uses an address match ‘/=$/’ as a conditional: If the current pattern space ends with a ‘=’, it reads the next input line using sed -i 's/hello/world/' file.txt71, replaces all ‘=’ characters which are followed by a newline, and unconditionally branches ( sed -n '1p ; $p' one.txt two.txt three.txt82) to the beginning of the program without restarting a new cycle. If the pattern space does not ends with ‘=’, the default action is performed: the pattern space is printed and a new cycle is started: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt02 Here’s an alternative program with a slightly different approach: On all lines except the last, sed -i 's/hello/world/' file.txt71 appends the line to the pattern space. A substitution command then removes soft line breaks (‘=’ at the end of a line, i.e. followed by a newline) by replacing them with an empty string. if the substitution was successful (meaning the pattern space contained a line which should be joined), The conditional branch command sed -n '1p ; $p' one.txt two.txt three.txt83 jumps to the beginning of the program without completing or restarting the cycle. If the substitution failed (meaning there were no soft line breaks), The sed -n '1p ; $p' one.txt two.txt three.txt83 command will not branch. Then, sed -n '1p ; $p' one.txt two.txt three.txt57 will print the pattern space content until the first newline, and sed -n '1p ; $p' one.txt two.txt three.txt39 will delete the pattern space content until the first new line. (To learn more about sed -i 's/hello/world/' file.txt71, sed -n '1p ; $p' one.txt two.txt three.txt57 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands see Multiline techniques). sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt03 For more line-joining examples see Joining lines. 7 Some Sample ScriptsHere are some sed -i 's/hello/world/' file.txt22 scripts to guide you in the art of mastering sed -i 's/hello/world/' file.txt22. 7.1 Joining linesThis section uses sed -i 's/hello/world/' file.txt71, sed -n '1p ; $p' one.txt two.txt three.txt39 and sed -n '1p ; $p' one.txt two.txt three.txt57 commands to process multiple lines, and the sed -n '1p ; $p' one.txt two.txt three.txt82 and sed -n '1p ; $p' one.txt two.txt three.txt83 commands for branching. See Multiline techniques and Branching and flow control. Join specific lines (e.g. if lines 2 and 3 need to be joined): sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt04 Join backslash-continued lines: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt05 Join lines that start with whitespace (e.g SMTP headers): sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt06 7.2 Centering LinesThis script centers all lines of a file on a 80 columns width. To change that width, the number in sed '30,35d' input.txt > output.txt39 must be replaced, and the number of added spaces also must be changed. Note how the buffer commands are used to separate parts in the regular expressions to be matched—this is a common technique. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt07 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt08 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt09 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt10 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt11 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt12 7.3 Increment a NumberThis script is one of a few that demonstrate how to do arithmetic in sed -i 's/hello/world/' file.txt22. This is indeed possible,9 but must be done manually. To increment one number you just add 1 to last digit, replacing it by the following digit. There is one exception: when the digit is a nine the previous digits must be also incremented until you don’t have a nine. This solution by Bruno Haible is very clever and smart because it uses a single buffer; if you don’t have this limitation, the algorithm used in Numbering lines, is faster. It works by replacing trailing nines with an underscore, then using multiple sed -n '1p ; $p' one.txt two.txt three.txt67 commands to increment the last digit, and then again substituting underscores with zeros. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt13 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt14 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt15 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt16 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt17 7.4 Rename Files to Lower CaseThis is a pretty strange use of sed -i 's/hello/world/' file.txt22. We transform text, and transform it to be shell commands, then just feed them to shell. Don’t worry, even worse hacks are done when using sed -i 's/hello/world/' file.txt22; I have seen a script converting the output of sed '30,35d' input.txt > output.txt44 into a sed '30,35d' input.txt > output.txt45 program! The main body of this is the sed -i 's/hello/world/' file.txt22 script, which remaps the name from lower to upper (or vice-versa) and even checks out if the remapped name is the same as the original name. Note how the script is parameterized using shell variables and proper quoting. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt18 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt19 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt20 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt21 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt22 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt23 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt24 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt25 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt26 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt27 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt28 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt29 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt30 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt31 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt32 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt33 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt34 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt35 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt36 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt37 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt38 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt39 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt40 7.5 Print sed '30,35d' input.txt > output.txt 47 EnvironmentThis script strips the definition of the shell functions from the output of the sed '30,35d' input.txt > output.txt48 Bourne-shell command. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt41 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt42 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt43 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt44 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt45 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt46 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt47 7.6 Reverse Characters of LinesThis script can be used to reverse the position of characters in lines. The technique moves two characters at a time, hence it is faster than more intuitive implementations. Note the sed '30,35d' input.txt > output.txt49 command before the definition of the label. This is often needed to reset the flag that is tested by the sed -n '1p ; $p' one.txt two.txt three.txt83 command. Imaginative readers will find uses for this script. An example is reversing the output of sed '30,35d' input.txt > output.txt51.10 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt48 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt49 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt50 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt51 7.7 Text search across multiple linesThis section uses sed -i 's/hello/world/' file.txt71 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands to search for consecutive words spanning multiple lines. See Multiline techniques. These examples deal with finding doubled occurrences of words in a document. Finding doubled words in a single line is easy using GNU $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 387 and similarly with GNU sed -i 's/hello/world/' file.txt22: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt52
When the doubled word span two lines the above regular expression will not find them as $ echo 1 | sed '\%1%s21232' 3 $ echo 1 | sed --debug '\%1%s21232' SED PROGRAM: /1/ s/1/3/ INPUT: 'STDIN' line 1 PATTERN: 1 COMMAND: /1/ s/1/3/ PATTERN: 3 END-OF-CYCLE: 387 and sed -i 's/hello/world/' file.txt22 operate line-by-line. By using sed -i 's/hello/world/' file.txt71 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands, sed -i 's/hello/world/' file.txt22 can apply regular expressions on multiple lines (that is, multiple lines are stored in the pattern space, and the regular expression works on it): sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt53
See the GNU sed '30,35d' input.txt > output.txt64 manual for an alternative solution using sed '30,35d' input.txt > output.txt65 and sed '30,35d' input.txt > output.txt66 at https://gnu.org/s/coreutils/manual/html_node/Squeezing-and-deleting.html. 7.8 Line length adjustmentThis section uses sed -i 's/hello/world/' file.txt71 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands to search for consecutive words spanning multiple lines, and the sed -n '1p ; $p' one.txt two.txt three.txt82 command for branching. See Multiline techniques and Branching and flow control. This (somewhat contrived) example deal with formatting and wrapping lines of text of the following input file: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt54 The following sed program wraps lines at 40 characters: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt55 The wrapped output: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt56 7.9 Reverse Lines of FilesThis one begins a series of totally useless (yet interesting) scripts emulating various Unix commands. This, in particular, is a sed '30,35d' input.txt > output.txt70 workalike. Note that on implementations other than GNU sed -i 's/hello/world/' file.txt22 this script might easily overflow internal buffers. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt57 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt58 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt59 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt60 7.10 Numbering LinesThis script replaces ‘cat -n’; in fact it formats its output exactly like GNU sed '30,35d' input.txt > output.txt72 does. Of course this is completely useless and for two reasons: first, because somebody else did it in C, second, because the following Bourne-shell script could be used for the same purpose and would be much faster: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt61 It uses sed -i 's/hello/world/' file.txt22 to print the line number, then groups lines two by two using sed -i 's/hello/world/' file.txt71. Of course, this script does not teach as much as the one presented below. The algorithm used for incrementing uses both buffers, so the line is printed as soon as possible and then discarded. The number is split so that changing digits go in a buffer and unchanged ones go in the other; the changed digits are modified in a single step (using a sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt83 command). The line number for the next line is then composed and stored in the hold space, to be used in the next iteration. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt63 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt64 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt65 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt66 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt67 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt68 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt69 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt70 7.11 Numbering Non-blank LinesEmulating ‘cat -b’ is almost the same as ‘cat -n’—we only have to select which lines are to be numbered and which are not. The part that is common to this script and the previous one is not commented to show how important it is to comment sed -i 's/hello/world/' file.txt22 scripts properly... sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt72 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt73 7.12 Counting CharactersThis script shows another way to do arithmetic with sed -i 's/hello/world/' file.txt22. In this case we have to add possibly large numbers, so implementing this by successive increments would not be feasible (and possibly even more complicated to contrive than this script). The approach is to map numbers to letters, kind of an abacus implemented with sed -i 's/hello/world/' file.txt22. ‘a’s are units, ‘b’s are tens and so on: we simply add the number of characters on the current line as units, and then propagate the carry to tens, hundreds, and so on. As usual, running totals are kept in hold space. On the last line, we convert the abacus form back to decimal. For the sake of variety, this is done with a loop rather than with some 80 sed -n '1p ; $p' one.txt two.txt three.txt67 commands11: first we convert units, removing ‘a’s from the number; then we rotate letters so that tens become ‘a’s, and so on until no more letters remain. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt75 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt76 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt77 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt78 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt79 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt80 7.13 Counting WordsThis script is almost the same as the previous one, once each of the words on the line is converted to a single ‘a’ (in the previous script each letter was changed to an ‘a’). It is interesting that real sed '30,35d' input.txt > output.txt80 programs have optimized loops for ‘wc -c’, so they are much slower at counting words rather than characters. This script’s bottleneck, instead, is arithmetic, and hence the word-counting one is faster (it has to manage smaller numbers). Again, the common parts are not commented to show the importance of commenting sed -i 's/hello/world/' file.txt22 scripts. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt82 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt83 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt84 7.14 Counting LinesNo strange things are done now, because sed -i 's/hello/world/' file.txt22 gives us ‘wc -l’ functionality for free!!! Look: 7.15 Printing the First LinesThis script is probably the simplest useful sed -i 's/hello/world/' file.txt22 script. It displays the first 10 lines of input; the number of displayed lines is right before the sed -n '1p ; $p' one.txt two.txt three.txt00 command. 7.16 Printing the Last LinesPrinting the last n lines rather than the first is more complex but indeed possible. n is encoded in the second line, before the bang character. This script is similar to the sed '30,35d' input.txt > output.txt70 script in that it keeps the final output in the hold space and prints it at the end: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt86 Mainly, the scripts keeps a window of 10 lines and slides it by adding a line and deleting the oldest (the substitution command on the second line works like a sed -n '1p ; $p' one.txt two.txt three.txt39 command but does not restart the loop). The “sliding window” technique is a very powerful way to write efficient and complex sed -i 's/hello/world/' file.txt22 scripts, because commands like sed -n '1p ; $p' one.txt two.txt three.txt57 would require a lot of work if implemented manually. To introduce the technique, which is fully demonstrated in the rest of this chapter and is based on the sed -i 's/hello/world/' file.txt71, sed -n '1p ; $p' one.txt two.txt three.txt57 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands, here is an implementation of sed '30,35d' input.txt > output.txt92 using a simple “sliding window.” This looks complicated but in fact the working is the same as the last script: after we have kicked in the appropriate number of lines, however, we stop using the hold space to keep inter-line state, and instead use sed -i 's/hello/world/' file.txt71 and sed -n '1p ; $p' one.txt two.txt three.txt39 to slide pattern space by one line: sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt07 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt88 Note how the first, second and fourth line are inactive after the first ten lines of input. After that, all the script does is: exiting on the last line of input, appending the next input line to pattern space, and removing the first line. 7.17 Make Duplicate Lines UniqueThis is an example of the art of using the sed -i 's/hello/world/' file.txt71, sed -n '1p ; $p' one.txt two.txt three.txt57 and sed -n '1p ; $p' one.txt two.txt three.txt39 commands, probably the most difficult to master. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt89 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt90 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt91 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt92 As you can see, we maintain a 2-line window using sed -n '1p ; $p' one.txt two.txt three.txt57 and sed -n '1p ; $p' one.txt two.txt three.txt39. This technique is often used in advanced sed -i 's/hello/world/' file.txt22 scripts. 7.18 Print Duplicated Lines of InputThis script prints only duplicated lines, like ‘uniq -d’. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt94 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt95 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt96 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt97 7.19 Remove All Duplicated LinesThis script prints only unique lines, like ‘uniq -u’. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt07 sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt99 sed -i 's/hello/world/' file.txt00 sed -i 's/hello/world/' file.txt01 sed -i 's/hello/world/' file.txt02 7.20 Squeezing Blank LinesAs a final example, here are three scripts, of increasing complexity and speed, that implement the same function as ‘cat -s’, that is squeezing blank lines. The first leaves a blank line at the beginning and end if there are some already. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt07 sed -i 's/hello/world/' file.txt04 sed -i 's/hello/world/' file.txt05 This one is a bit more complex and removes all empty lines at the beginning. It does leave a single blank line at end if one was there. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt07 sed -i 's/hello/world/' file.txt07 sed -i 's/hello/world/' file.txt08 This removes leading and trailing blank lines. It is also the fastest. Note that loops are completely done with sed -n '1p ; $p' one.txt two.txt three.txt52 and sed -n '1p ; $p' one.txt two.txt three.txt82, without relying on sed -i 's/hello/world/' file.txt22 to restart the script automatically at the end of a line. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt62 sed -i 's/hello/world/' file.txt10 sed -i 's/hello/world/' file.txt11 sed -i 's/hello/world/' file.txt12 sed -i 's/hello/world/' file.txt13 sed -i 's/hello/world/' file.txt14 8 GNU sed -i 's/hello/world/' file.txt 22’s Limitations and Non-limitationsFor those who want to write portable sed -i 's/hello/world/' file.txt22 scripts, be aware that some implementations have been known to limit line lengths (for the pattern and hold spaces) to be no more than 4000 bytes. The POSIX standard specifies that conforming sed -i 's/hello/world/' file.txt22 implementations shall support at least 8192 byte line lengths. GNU sed -i 's/hello/world/' file.txt22 has no built-in limit on line length; as long as it can sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt008 more (virtual) memory, you can feed or construct lines as long as you like. However, recursion is used to handle subpatterns and indefinite repetition. This means that the available stack space may limit the size of the buffer that can be processed by certain patterns. 9 Other Resources for Learning About sed -i 's/hello/world/' file.txt 22For up to date information about GNU sed -i 's/hello/world/' file.txt22 please visit https://www.gnu.org/software/sed/. Send general questions and suggestions to [email protected]. Visit the mailing list archives for past discussions at https://lists.gnu.org/archive/html/sed-devel/. The following resources provide information about sed -i 's/hello/world/' file.txt22 (both GNU sed -i 's/hello/world/' file.txt22 and other variations). Note these not maintained by GNU sed -i 's/hello/world/' file.txt22 developers. 10 Reporting BugsEmail bug reports to [email protected]. Also, please include the output of ‘sed --version’ in the body of your report if at all possible. Please do not send a bug report like this: sed -i 's/hello/world/' file.txt15 If GNU sed -i 's/hello/world/' file.txt22 doesn’t configure your favorite package, take a few extra minutes to identify the specific problem and make a stand-alone test case. Unlike other programs such as C compilers, making such test cases for sed -i 's/hello/world/' file.txt22 is quite simple. A stand-alone test case includes all the data necessary to perform the test, and the specific invocation of sed -i 's/hello/world/' file.txt22 that causes the problem. The smaller a stand-alone test case is, the better. A test case should not involve something as far removed from sed -i 's/hello/world/' file.txt22 as “try to configure frobme-1.3.4”. Yes, that is in principle enough information to look for the bug, but that is not a very practical prospect. Here are a few commonly reported bugs that are not bugs. sed -i 's/hello/world/' file.txt71 command on the last line Most versions of sed -i 's/hello/world/' file.txt22 exit without printing anything when the sed -i 's/hello/world/' file.txt71 command is issued on the last line of a file. GNU sed -i 's/hello/world/' file.txt22 prints pattern space before exiting unless of course the sed -i 's/hello/world/' file.txt45 command switch has been specified. This choice is by design. Default behavior (gnu extension, non-POSIX conforming): To force POSIX-conforming behavior: sed -i 's/hello/world/' file.txt16 For example, the behavior of would depend on whether foo has an even or an odd number of lines12. Or, when writing a script to read the next few lines following a pattern match, traditional implementations of sed -i 's/hello/world/' file.txt22 would force you to write something like sed -i 's/hello/world/' file.txt17 instead of just sed -i 's/hello/world/' file.txt18 In any case, the simplest workaround is to use sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt024 in scripts that rely on the traditional behavior, or to set the sed -i 's/hello/world/' file.txt72 variable to a non-empty value.Regex syntax clashes (problems with backslashes) sed -i 's/hello/world/' file.txt22 uses the POSIX basic regular expression syntax. According to the standard, the meaning of some escape sequences is undefined in this syntax; notable in the case of sed -i 's/hello/world/' file.txt22 are # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE11, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE23, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE25, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt56, sed 's/hello/world/' input.txt > output.txt sed -e 's/hello/world/' input.txt > output.txt sed --expression='s/hello/world/' input.txt > output.txt echo 's/hello/world/' > myscript.sed sed -f myscript.sed input.txt > output.txt sed --file=myscript.sed input.txt > output.txt57, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE91, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE92, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE87, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE88, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE85, and # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE86. As in all GNU programs that use POSIX basic regular expressions, sed -i 's/hello/world/' file.txt22 interprets these escape sequences as special characters. So, sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt040 matches one or more occurrences of ‘x’. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt041 matches either ‘abc’ or ‘def’. This syntax may cause problems when running scripts written for other sed -i 's/hello/world/' file.txt22s. Some sed -i 's/hello/world/' file.txt22 programs have been written with the assumption that # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE11 and # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE23 match the literal characters sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt046 and sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt047. Such scripts must be modified by removing the spurious backslashes if they are to be used with modern implementations of sed -i 's/hello/world/' file.txt22, like GNU sed -i 's/hello/world/' file.txt22. On the other hand, some scripts use s|abc\|def||g to remove occurrences of either sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt050 or sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt051. While this worked until sed -i 's/hello/world/' file.txt22 4.0.x, newer versions interpret this as removing the string sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt053. This is again undefined behavior according to POSIX, and this interpretation is arguably more robust: older sed -i 's/hello/world/' file.txt22s, for example, required that the regex matcher parsed sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt055 as sed -n '1p ; $p' one.txt two.txt three.txt94 in the common case of escaping a slash, which is again undefined behavior; the new behavior avoids this, and this is good because the regex matcher is only partially under our control. In addition, this version of sed -i 's/hello/world/' file.txt22 supports several escape characters (some of which are multi-character) to insert non-printable characters in scripts ( $ echo | sed 'Q42' ; echo $? 4202, sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt059, sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt060, sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt061, $ echo | sed 'Q42' ; echo $? 4205, # WRONG USAGE: 'FILE' will be truncated. sed -ni 's/foo/bar/' FILE53, $ echo | sed 'Q42' ; echo $? 4207, sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt065). These can cause similar problems with scripts written for other sed -i 's/hello/world/' file.txt22s.-i clobbers read-only files In short, ‘sed -i’ will let you delete the contents of a read-only file, and in general the -i option (see Invocation) lets you clobber protected files. This is not a bug, but rather a consequence of how the Unix file system works. The permissions on a file say what can happen to the data in that file, while the permissions on a directory say what can happen to the list of files in that directory. ‘sed -i’ will not ever open for writing a file that is already on disk. Rather, it will work on a temporary file that is finally renamed to the original name: if you rename or delete files, you’re actually modifying the contents of the directory, so the operation depends on the permissions of the directory, not of the file. For this same reason, sed -i 's/hello/world/' file.txt22 does not let you use -i on a writable file in a read-only directory, and will break hard or symbolic links when -i is used on such a file. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt068 does not work (gives an error) There is no line 0. 0 is a special address that is only used to treat addresses like sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt069 as active when the script starts: if you write sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt070 and the first line includes the word ‘abc’, then that match would be ignored because address ranges must span at least two lines (barring the end of the file); but what you probably wanted is to delete every line up to the first one including ‘abc’, and this is obtained with sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt071. sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt072 is case insensitive You are encountering problems with locales. POSIX mandates that sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt072 uses the current locale’s collation order – in C parlance, that means using sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt074 instead of sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt075. Some locales have a case-insensitive collation order, others don’t. Another problem is that sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt072 tries to use collation symbols. This only happens if you are on the GNU system, using GNU libc’s regular expression matcher instead of compiling the one supplied with GNU sed. In a Danish locale, for example, the regular expression sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt077 matches the string ‘aa’, because this is a single collating symbol that comes after ‘a’ and before ‘b’; ‘ll’ behaves similarly in Spanish locales, or ‘ij’ in Dutch locales. To work around these problems, which may cause bugs in shell scripts, set the sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt078 and $ echo | sed 'Q42' ; echo $? 4246 environment variables to ‘C’. $ echo | sed 'Q42' ; echo $? 4226 does not clear pattern space This happens if your input stream includes invalid multibyte sequences. POSIX mandates that such sequences are not matched by ‘.’, so that ‘s/.*//’ will not clear pattern space as you would expect. In fact, there is no way to clear sed’s buffers in the middle of the script in most multibyte locales (including UTF-8 locales). For this reason, GNU sed -i 's/hello/world/' file.txt22 provides a ‘z’ command (for ‘zap’) as an extension. To work around these problems, which may cause bugs in shell scripts, set the sed 's/hello/world/' input.txt > output.txt sed 's/hello/world/' < input.txt > output.txt cat input.txt | sed 's/hello/world/' - > output.txt078 and $ echo | sed 'Q42' ; echo $? 4246 environment variables to ‘C’. Appendix A GNU Free Documentation LicenseVersion 1.3, 3 November 2008 sed -i 's/hello/world/' file.txt19
ADDENDUM: How to use this License for your documentsTo use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: sed -i 's/hello/world/' file.txt20 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this: sed -i 's/hello/world/' file.txt21 If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software. Concept IndexThis is a general index of all issues discussed in this manual, with the exception of the sed -i 's/hello/world/' file.txt22 commands and command-line options. |
