sed(C)
sed -- invoke the stream editor
Syntax
sed [
-n ] [
script ] [
-f
sfile ] [
file ... ]
sed [ -n ] [ -e script ] ... [ -f
sfile ] ... [ file ... ]
Description
The
sed command copies the named
files
(standard input default) to the standard output, edited according to a script of
commands.
sed takes the following options:
- -e script
- Read the command script; usually quoted to protect it from the
shell.
- -f sfile
- Take the script from the file sfile; these options accumulate. If
there is just one -e option and no -f options, the flag
-e may be omitted.
- -n
- Suppress the default output.
A
script consists of editing
commands, one per line, of the following form:
[
address [ ,
address ] ]
function [
arguments ]
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.
A semicolon ``;'' can be used as a command delimiter.
Some of the commands use a hold space to save all or part of the pattern
space for subsequent retrieval (see the ``Limitations'' section).
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, that is, a /regular expression/ as described in regexp(M),
modified as follows:
- In a context address, the construction \?regular expression?, where
``?'' is any character, is identical to /regular expression/. Note that
in the context address \xabc\xdefx, the second x stands for
itself, so that the standard expression is abcxdef.
- The escape sequence \n matches a newline embedded in the pattern space.
- A dot (.) matches any character except the terminal newline of 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 separated by a comma 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 only to nonselected
pattern spaces by use of the negation function ``!'' described in the next
section.
Functions
In the following list of functions, the maximum number of
permissible addresses for each function is indicated in parentheses.
The text argument consists of one or more lines, all but the last of
which end with backslashes to hide the newlines. 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.
The rfile or wfile argument must terminate the command line and
must be preceded by one blank. Each wfile is created before processing
begins. There can be at most 10 distinct wfile arguments.
- (1) a\
text
- Appends text, placing it on the output before reading the next
input line. Note that there must be a line break between the command and the
text.
- (2) b label
- Branches to the : command bearing the label. If label
is empty, branches to the end of the script.
- (2) c\
text
- Changes text by deleting the pattern space and then appending text.
With 0 or 1 address or at the end of a 2-address range, places text on
the output and starts the next cycle. Note that there must be a line break
between the command and the text.
- (2) d
- Deletes the pattern space and starts the next cycle.
- (2) D
- Deletes the initial segment of the pattern space through the first newline
and starts the next cycle.
- (2) g
- Replaces the contents of the pattern space with the contents of the hold
space.
- (2) G
- Appends the contents of the hold space to the pattern space.
- (2) h
- Replaces the contents of the hold space with the contents of the pattern
space.
- (2) H
- Appends the contents of the pattern space to the hold space.
- (1) i\
text
- Insert. Places text on the standard output. Note that there must be
a line break between the command and the text.
- (2) l
- Lists the pattern space on the standard output in an unambiguous way.
Nonprinting characters are displayed as a three digit octal number preceded by
a backslash ``\''. The following characters are printed as escape sequences:
-------------------------------------------
Character Output
-------------------------------------------
backslash \\
alert (bell) \a
backspace \b
form feed \f
carriage return \r
horizontal tab \t
vertical tab \v
Any output lines that are longer than the output device width
(determined by the environment variable COLUMNS) are folded into multiple
lines. New lines, inserted when folding a long line, are escaped by a
preceding backslash character. The ends of each line in the pattern space are
denoted by a dollar character ``$''.
- (2) n
- Copies the pattern space to the standard output. Replaces the pattern
space with the next line of input.
- (2) N
- Appends the next line of input to the pattern space with an embedded
newline. (The current line number changes.)
- (2) p
- Prints (copies) the pattern space on the standard output.
- (2) P
- Prints (copies) the initial segment of the pattern space through the first
newline to the standard output.
- (1) q
- Quits sed by branching to the end of the script. No new cycle is
started.
- (2) r rfile
- Reads the contents of rfile and places them on the output before
reading the next input line.
- (2) s /regular expression/replacement/flags
- Substitutes the replacement string for instances of the regular
expression in the pattern space. Any character may be used instead of
``/''. For a more detailed description, see regexp(M).
Flags is zero or more of:
- n
- Substitute for just the nth occurrence of the regular
expression. n must be an integer greater than zero.
- g
- Globally substitutes for all non-overlapping instances of the regular
expression rather than just the first one.
- p
- Prints the pattern space if a replacement was made.
- w wfile
- Writes the pattern space to wfile if a replacement was made.
- (2) t label
- Branches to the colon (:) command bearing label if any
substitutions have been made since the most recent reading of an input line or
execution of a t command. If label is empty, t branches
to the end of the script.
- (2) w wfile
- Writes the pattern space to wfile.
- (2) x
- Exchanges the contents of the pattern and hold spaces.
- (2) y /string1/string2/
- Replaces all occurrences of characters in string1 with the
corresponding characters in string2. The lengths of string1 and
string2 must be equal.
- (2) ! function
- Applies the function (or group, if function is ``{'') only
to lines not selected by the address(es).
- (0) : label
- This command does nothing; it bears a label for b and
t commands to branch to. Labels can be at most 8 characters long.
- (1) =
- Places the current line number on the standard output as a line.
- (2) {
- Executes the following commands through a matching ``}'' only when the
pattern space is selected.
- (2) !{
- Executes the following commands through a matching ``}'' only when the
pattern space is not selected.
- (0)
- An empty command is ignored.
- (0) #
- Ignore the remainder of the line if # is followed by any other
character than ``n'' (treat the line as a comment); if the character ``n''
follows #, suppress the default output (equivalent to the command line
option -n).
Environment variables
- COLUMNS
- The width of the standard output device in characters; used by the
l command for folding long lines. If this variable is not set or it has
an invalid value, sed uses the default value 72.
Exit values
sed continues to process all
file arguments
even if one or more of them produces an open error. If there is an open error,
sed will exit with a value of 1 when it has finished processing the
files. A value of 2 indicates a usage error.
Examples
The following examples assume the use of
sh(C)
or
ksh(C).
A common use of sed is to edit a file from within a shell script. In
this example, every occurrence of the string ``sysman'' in the file
infile is replaced by ``System Manager''. A temporary file TMP is used to
hold the intermediate result of the edit:
TMP=/usr/tmp/tmpfile_$$
sed -e 's/sysman/System Manager/g' < infile > $TMP
mv $TMP infile
In this example,
sed removes all blank lines (including those with
just <Tab> and <Space> characters) from
padded_file:
sed '
/^$/ d
/^[<Tab><Space>]*$/ d
´ padded_file
sed can be used to strip all lines from a file which do not contain
a certain string. In this example, all lines in the file
infile which
start with a hash ``#'' are echoed to the screen:
sed -e '/^#/!d'
< infile
If several editing commands must be carried out on a file, but the parameters
for the edit are to be supplied by the user, then use echo to append
command lines to a sed script. The following example removes all
occurrences of the strings given as arguments to the script from the file
infile. The name of the temporary file is held by the variable SCRIPT:
SCRIPT=/usr/tmp/script_$$
for name in $*
do
echo "s/${name}//g" >> $SCRIPT
done
TMPFILE=/usr/tmp/tmpfile_$$
sed -f $SCRIPT < infile > $TMPFILE
mv $TMPFILE infile
rm $SCRIPT
Another use of
sed is to process the output from other
commands. Here the
ps command is filtered using
sed to report the
status of all processes other than those owned by the super user:
ps
-ef | sed -e '/^[<Space><Tab>]*root/d'
Limitations
Both the hold space and pattern space can hold a maximum of
8192 bytes.
See also
awk(C),
ed(C),
grep(C),
regexp(M)
Chapter
14, ``Manipulating text with sed'' in the Operating System User's
Guide
Standards conformance
sed is conformant with:
ISO/IEC DIS 9945-2:1992, Information technology - Portable Operating System
Interface (POSIX) - Part 2: Shell and Utilities (IEEE Std 1003.2-1992);
AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities,
Issue 4, 1992.
SCO OpenServer Release 5.0.6 -- 1 August 2000