SED(1) SED(1)
NAME
sed - stream editor
SYNOPSIS
sed [ -n ] [ -g ] [ -u ] [ -e script ] [ -f sfile ] [ file
... ]
DESCRIPTION
Sed copies the named files (standard input default) to the
standard output, edited according to a script of commands.
The -f option causes the script to be taken from file sfile;
these options accumulate. If there is just one -e option
and no -f's, the option -e may be omitted. The -n option
suppresses the default output; -g causes all substitutions
to be global, as if suffixed g. If -u is specified, sed
flushes its output buffers before reading in further input.
A script consists of editing commands, one per line, of the
following form:
[address [, address] ] function [argument ...] [;]
In normal operation sed cyclically copies a line of input
into a pattern space (unless there is something left after a
`D' command), applies in sequence all commands whose
addresses select that pattern space, and at the end of the
script copies the pattern space to the standard output
(except under -n) and deletes the pattern space.
An address is either a decimal number that counts input
lines cumulatively across files, a `$' that addresses the
last line of input, or a context address,
/regular-expression/, in the style of regexp(6), with the
added convention that `\n' matches a newline embedded in the
pattern space.
A command line with no addresses selects every pattern
space.
A command line with one address selects each pattern space
that matches the address.
A command line with two addresses selects the inclusive
range from the first pattern space that matches the first
address through the next pattern space that matches the sec-
ond. (If the second address is a number less than or equal
to the line number first selected, only one line is
selected.) Thereafter the process is repeated, looking
again for the first address.
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Editing commands can be applied to non-selected pattern
spaces by use of the negation function `!' (below).
An argument denoted text consists of one or more lines, all
but the last of which end with `\' to hide the newline.
Backslashes in text are treated like backslashes in the
replacement string of an `s' command, and may be used to
protect initial blanks and tabs against the stripping that
is done on every script line.
An argument denoted rfile or wfile must terminate the com-
mand line and must be preceded by exactly one blank. Each
wfile is created before processing begins. There can be at
most 120 distinct wfile arguments.
a\
text Append. Place text on the output before read-
ing the next input line.
b label Branch to the : command bearing the label. If
label is empty, branch to the end of the
script.
c\
text Change. Delete the pattern space. With 0 or 1
address or at the end of a 2-address range,
place text on the output. Start the next
cycle.
d Delete the pattern space. Start the next
cycle.
D Delete the initial segment of the pattern space
through the first newline. Start the next
cycle.
g Replace the contents of the pattern space by
the contents of the hold space.
G Append the contents of the hold space to the
pattern space.
h Replace the contents of the hold space by the
contents of the pattern space.
H Append the contents of the pattern space to the
hold space.
i\
text Insert. Place text on the standard output.
n Copy the pattern space to the standard output.
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Replace the pattern space with the next line of
input.
N Append the next line of input to the pattern
space with an embedded newline. (The current
line number changes.)
p Print. Copy the pattern space to the standard
output.
P Copy the initial segment of the pattern space
through the first newline to the standard out-
put.
q Quit. Branch to the end of the script. Do not
start a new cycle.
r rfile Read the contents of rfile. Place them on the
output before reading the next input line.
s/regular-expression/replacement/flags
Substitute the replacement string for instances
of the regular-expression in the pattern space.
Any character may be used instead of `/'. For
a fuller description see regexp(6). Flags is
zero or more of
g Global. Substitute for all non-
overlapping instances of the regular
expression rather than just the first one.
p Print the pattern space if a replacement
was made.
w wfile
Write. Append the pattern space to wfile
if a replacement was made.
An ampersand `&' appearing in the replacement
is replaced by the string matching the regular
expression. The characters \n, where n is a
digit, are replaced by the text matched by the
n-th regular subexpression enclosed between `('
and `)'. When nested parenthesized subexpres-
sions are present, n is determined by counting
occurrences of `(' starting from the left.
t label Test. Branch to the `:' command bearing the
label if any substitutions have been made since
the most recent reading of an input line or
execution of a `t'. If label is empty, branch
to the end of the script.
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w wfile
Write. Append the pattern space to wfile.
x Exchange the contents of the pattern and hold
spaces.
y/string1/string2/
Transform. Replace all occurrences of charac-
ters in string1 with the corresponding charac-
ter in string2. The lengths of string1 and
string2 must be equal.
!function Don't. Apply the function (or group, if
function is `{') only to lines not selected by
the address(es).
# Comment. Ignore the rest of the line.
: label This command does nothing; it bears a label for
b and t commands to branch to.
= Place the current line number on the standard
output as a line.
{ Execute the following commands through a match-
ing `}' only when the pattern space is
selected.
An empty command is ignored.
EXAMPLES
sed 10q file
Print the first 10 lines of the file.
sed '/^$/d'
Delete empty lines from standard input.
sed 's/UNIX/& system/g'
Replace every instance of `UNIX' by `UNIX system'.
sed 's/ *$// drop trailing blanks
/^$/d drop empty lines
s/ */\ replace blanks by newlines
/g
/^$/d' chapter*
Print the files chapter1, chapter2, etc. one word to a
line.
nroff -ms manuscript | sed '
${
/^$/p if last line of file is empty, print it
}
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//N if current line is empty, append next line
/^\n$/D' if two lines are empty, delete the first
Delete all but one of each group of empty lines from a
formatted manuscript.
SOURCE
/sys/src/cmd/sed.c
SEE ALSO
ed(1), grep(1), awk(1), lex(1), sam(1), regexp(6)
L. E. McMahon, `SED - A Non-interactive Text Editor', Unix
Research System Programmer's Manual, Volume 2.
BUGS
If input is from a pipe, buffering may consume characters
beyond a line on which a `q' command is executed.
-u does not work as expected if $ addressing is used.
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