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NAME
SYNOPSIS
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sed [ −gln ] [ −e script ] [ −f sfile ] [ file ... ]
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DESCRIPTION
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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:
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[address [, address] ] function [argument ...]
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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(7), 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 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 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 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
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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 wfileWrite. Append the pattern space to wfile if a replacement
was made.
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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.
w wfile
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Write. Append the pattern space to wfile.
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x Exchange the contents of the pattern and hold spaces.
y/string1/string2/
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Transform. Replace all occurrences of characters in string1 with
the corresponding character in string2. The lengths of string1
and string2 must be equal.
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!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.
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An empty command is ignored.
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EXAMPLES
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sed 10q file
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Print the first 10 lines of the file.
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sed '/^$/d'
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Delete empty lines from standard input.
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sed 's/UNIX/& system/g'
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Replace every instance of UNIX by UNIX system.
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sed 's/ *$// drop trailing blanks
/^$/d drop empty lines
s/ */\ replace blanks by newlines
/g
/^$/d' chapter*
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Print the files chapter1, chapter2, etc. one word to a line.
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nroff −ms manuscript | sed '
${
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if last line of file is empty, print it
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}
//N if current line is empty, append next line
/^\n$/D' if two lines are empty, delete the first
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Delete all but one of each group of empty lines from a formatted
manuscript.
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SOURCE
SEE ALSO
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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.
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BUGS
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If input is from a pipe, buffering may consume characters beyond
a line on which a q command is executed.
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