NAME
sed - stream editor
SYNOPSIS
sed [ -gln ] [ -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 flag -e may be omitted.
The -n option suppresses the default output; -g causes all
substitutions to be global, as if suffixed g. The -l option causes sed
to flush its output buffer after every newline.
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 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(7),
with the added convention that 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 second. (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.
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 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 command 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 reading 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. 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 output.
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(7). 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.
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 If label is empty,
branch to the end of the script.
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 characters in
string1 with the corresponding character 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).
: 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 matching 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 ’/^$/d’
Delete empty lines from standard input.
sed ’s/UNIX/& system/g’
Replace every instance of by
sed ’s/ *$// 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 } //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
/src/cmd/sed.c
SEE ALSO
ed(1), grep(1), awk(1), lex(1), sam(1), regexp(7)
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 command is executed.
SED(1)