SED

Section: User Commands (1)
Updated: 1998-05-07
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This file is part of GNU sed.
Copyright (C) 1998 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

NAME

sed - a Stream EDitor

SYNOPSIS

sed [-n] [-V] [--quiet] [--silent] [--version] [--help]
    [-e script] [--expression=script]
    [-f script-file] [--file=script-file]
    [script-if-no-other-script]
    [file...]

DESCRIPTION

Sed 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 ed), sed works by making only one pass over the input(s), and is consequently more efficient. But it is sed's ability to filter text in a pipeline which particularly distinguishes it from other types of editors.

OPTIONS

Sed may be invoked with the following command-line options:

-V
--version: Print out the version of sed that is being run and a copyright notice, then exit.
-h
--help: Print a usage message briefly summarizing these command-line options and the bug-reporting address, then exit.
-n
--quiet
--silent: By default, sed will print out the pattern space at the end of each cycle through the script. These options disable this automatic printing, and sed will only produce output when explicitly told to via the p command.
-e script
--expression=script: Add the commands in script to the set of commands to be run while processing the input.
-f script-file
--file=script-file: Add the commands contained in the file script-file to the set of commands to be run while processing the input.

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 processed if no file names are specified.

Command Synopsis

This is just a brief synopsis of sed commands to serve as a reminder to those who already know sed; other documentation (such as the texinfo document) must be consulted for fuller descriptions.

Zero-address ``commands''

: label: Label for b and t commands.
#comment: The comment extends until the next newline (or the end of a -e script fragment).
}: The closing bracket of a { } block.

Zero- or One- address commands

=: Print the current line number.
a \
text: Append text, which has each embedded newline preceeded by a backslash.
i \
text: Insert text, which has each embedded newline preceeded by a backslash.
q: Immediately quit the sed script without processing any more input, except that if auto-print is not diabled the current pattern space will be printed.
r filename: Append text read from filename.

Commands which accept address ranges

{: Begin a block of commands (end with a }).
b label: Branch to label; if label is omitted, branch to end of script.
t label: If a s/// has done a successful substitution since the last input line was read and since the last t command, then branch to label; if label is omitted, branch to end of script.
c \
text: Replace the selected lines with text, which has each embedded newline preceeded by a backslash.
d: Delete pattern space. Start next cycle.
D: Delete up to the first embedded newline in the pattern space. Start next cycle, but skip reading from the input if there is still data in the pattern space.
h H: Copy/append pattern space to hold space.
g G: Copy/append hold space to pattern space.
x: Exchange the contents of the hold and pattern spaces.
l: List out the current line in a ``visually unambiguous'' form.
n N: Read/append the next line of input into the pattern space.
p: Print the current pattern space.
P: Print up to the first embedded newline of the current pattern space.
s/regexp/replacement/: Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp.
w: filename Write the current pattern space to filename.
y/source/dest/: Transliterate the characters in the pattern space which appear in source to the corresponding character in dest.

Addresses

Sed commands can be given with no addresses, in which case the command will be executed for all input lines; with one address, in which case the command will only be executed for input lines which match that address; or with two addresses, in which case the command will be executed for all input lines which match the inclusive range of lines starting from the first address and continuing to the second address. Three things to note about address ranges: the syntax is addr1,addr2 (i.e., the addresses are separated by a comma); the line which addr1 matched will always be accepted, even if addr2 selects an earlier line; and if addr2 is a regexp, it will not be tested against the line that addr1 matched.

After the address (or address-range), and before the command, a ! may be inserted, which specifies that the command shall only be executed if the address (or address-range) does not match.

The following address types are supported:

number: Match only the specified line number.
first~step: Match every step'th line starting with line first. For example, ``sed -n 1~2p'' will print all the odd-numbered lines in the input stream, and the address 2~5 will match every fifth line, starting with the second. (This is a GNU extension.)
$: Match the last line.
/regexp/: Match lines matching the regular expression regexp.
\cregexpc: Match lines matching the regular expression regexp. The c may be any character.

Regular expressions

POSIX.2 BREs should be supported, but they aren't completely yet. The \n sequence in a regular expression matches the newline character. There are also some GNU extensions. [XXX FIXME: more needs to be said. At the very least, a reference to another document which describes what is supported should be given.]

Miscellaneous notes

This version of sed supports a \<newline> sequence in all regular expressions, the replacement part of a substitute (s) command, and in the source and dest parts of a transliterate (y) command. The \ is stripped, and the newline is kept.

BUGS

E-mail bug reports to bug-gnu-utils@gnu.org. Be sure to include the word ``sed'' somewhere in the ``Subject:'' field.

Addresses

Regular expressions

Miscellaneous notes

SEE ALSO

BUGS

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