sed - Online in the Cloud

PROGRAM:

NAME

sed - stream editor for filtering and transforming text

SYNOPSIS

sed [OPTION]... {script-only-if-no-other-script} [input-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.

-n, --quiet, --silent

suppress automatic printing of pattern space

-e script, --expression=script

add the script to the commands to be executed

-f script-file, --file=script-file

add the contents of script-file to the commands to be executed

--follow-symlinks

follow symlinks when processing in place

-i[SUFFIX], --in-place[=SUFFIX]

edit files in place (makes backup if SUFFIX supplied)

-l N, --line-length=N

specify the desired line-wrap length for the `l' command

--posix

disable all GNU extensions.

-r, --regexp-extended

use extended regular expressions in the script.

-s, --separate

consider files as separate rather than as a single continuous long stream.

-u, --unbuffered

load minimal amounts of data from the input files and flush the output buffers more
often

-z, --null-data

separate lines by NUL characters

--help
display this help and exit

--version
output version information and exit

If no -e, --expression, -f, or --file option is given, then the first non-option argument
is taken as the sed script to interpret. All remaining arguments are names of input
files; if no input files are specified, then the standard input is read.

GNU sed home page: <http://www.gnu.org/software/sed/>. General help using GNU software:
<http://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. Be sure to
include the word ``sed'' somewhere in the ``Subject:'' field.

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 preceded by a backslash.

i

text Insert text, which has each embedded newline preceded by a backslash.

q [exit-code]
Immediately quit the sed script without processing any more input, except that if
auto-print is not disabled the current pattern space will be printed. The exit
code argument is a GNU extension.

Q [exit-code]
Immediately quit the sed script without processing any more input. This is a GNU
extension.

r filename
Append text read from filename.

R filename
Append a line read from filename. Each invocation of the command reads a line from
the file. This is a GNU extension.

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.

c

text Replace the selected lines with text, which has each embedded newline preceded by a
backslash.

d Delete pattern space. Start next cycle.

D If pattern space contains no newline, start a normal new cycle as if the d 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.

h H Copy/append pattern space to hold space.

g G Copy/append hold space to pattern space.

l List out the current line in a ``visually unambiguous'' form.

l width
List out the current line in a ``visually unambiguous'' form, breaking it at width
characters. This is a GNU extension.

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.

t label
If a s/// has done a successful substitution since the last input line was read and
since the last t or T command, then branch to label; if label is omitted, branch to
end of script.

T label
If no s/// has done a successful substitution since the last input line was read
and since the last t or T command, then branch to label; if label is omitted,
branch to end of script. This is a GNU extension.

w filename
Write the current pattern space to filename.

W filename
Write the first line of the current pattern space to filename. This is a GNU
extension.

x Exchange the contents of the hold and pattern spaces.

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 (which increments cumulatively across files,
unless the -s option is specified on the command line).

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. first can be zero; in this case,
sed operates as if it were equal to step. (This is an 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.

GNU sed also supports some special 2-address forms:

0,addr2
Start out in "matched first address" state, until addr2 is found. This is similar
to 1,addr2, except that if addr2 matches the very first line of input the 0,addr2
form will be at the end of its range, whereas the 1,addr2 form will still be at the
beginning of its range. This works only when addr2 is a regular expression.

addr1,+N
Will match addr1 and the N lines following addr1.

addr1,~N
Will match addr1 and the lines following addr1 until the next line whose input line
number is a multiple of N.

REGULAR EXPRESSIONS

POSIX.2 BREs should be supported, but they aren't completely because of performance
problems. The \n sequence in a regular expression matches the newline character, and
similarly for \a, \t, and other sequences.

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