sed - stream editor
sed [
-gln ] [
-e script ] [
-f sfile
] [
file ... ]
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.
- 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.
/src/cmd/sed.c
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.
If input is from a pipe, buffering may consume characters beyond a line on which
a command is executed.