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Stream editor (POSIX)
sed [[-n] script [file...]
sed [-n] [-e script]... [-f script_file]... [-V]
[file...]
QNX Neutrino, Microsoft Windows
- -e script
- Use the command-line script for editing
files. If you specify multiple -e
options, the scripts are applied in the order
specified to each line of the input files. If a -f
option is specified in addition to -e, lines are acted
upon by scripts first.
- -f script_file
- Use the file script_file as the script of editing
instructions. If multiple -f options are specified, the
scripts are applied in the order specified to each
line of the input files. If a -e option is specified in
addition to -f, lines are acted upon by
scripts first.
- -n
- Suppress the default output, which passes each line to standard output
after it's examined for editing. Only lines explicitly selected for output
are written.
- -V
- Display the version number, and exit.
- file
- The pathname of a text file whose contents are read and edited. If you
specify multiple files, the files are read in the order specified and the
concatenation is edited. If no files are specified, the standard input is
used.
- script
- A script consists of one or more editing
instructions that you enter on the command line.
The sed utility is a stream editor that reads one or
more text files, makes editing changes according to editing commands
that you specify, and writes the results to standard output.
|
This utility is subject to the GNU Public License (GPL).
We've included it for use on development systems. |
The sed commands are usually stored in a program file
(script_file), although you may give simple sed
commands from the command line. By default, sed copies files from
the file list to its standard output, editing the lines in the process.
Conceptually, there is one input file, which is the concatenation of
all input files specified.
Lines are selected for editing based on their position within the
input file, or by pattern matching. If no files are listed, input is taken
from standard input (this is the only time standard input is used). The
sed utility initially reads all the editing commands from all
specified sources and places them in an internal table in the order specified.
The utility then processes the (concatenated) input file as follows:
- Read one line from the input file and copy to the
pattern space (a work area).
- For each command that selects the line, act on the pattern space as the
edit command specifies, cyclically placing the result into the pattern
space.
- After all commands have been checked against the pattern space, write the
pattern space to the standard output, provided -n
was not specified. The pattern space may contain zero, one,
or several lines at this time.
- Delete the contents of the pattern space.
- Repeat from step 1 until all of the (concatenated) input file has been
read and processed.
A script consists of editing commands, one per line,
of the following form:
[address[,address]]function[arguments]
You can specify the script of editing commands in the
command line, or it can be contained in the file script_file.
In default 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.
Some of the commands use a hold space to save all or
part of the pattern space for subsequent retrieval. The
pattern and hold spaces are each
limited to 20K.
An address is one of the following:
- a decimal number that counts input lines cumulatively across files
- a $ token that addresses the last line of input
- a context address
- a regular expression
A command line with no address 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 address. (If the line number
of the second address is less than or equal to the line number first selected,
then only the first line is selected.) Starting at the first line
following the selected range, sed looks again for the
first address. Thereafter the process is repeated.
You can use the negation character (!) to apply editing commands
to non-selected pattern spaces.
For more information, see
“Editing commands,” below.
The sed utility uses basic regular expressions (REs),
with the following additions:
- In a context address, the construction
\?RE?
(where ? is any character) is mapped to
/RE/.
Note that in the context address \xabc\xdefx, the second
x stands for itself, so that the regular expression is
abcxdef.
- The escape sequence \n matches a newline
embedded in the pattern space.
- A period (.) matches any character except the last
newline of the pattern space.
In the following list of functions, the maximum number of permissible addresses
for each function is indicated by one of [0addr],
[1addr] or [2addr] representing a maximum of
zero addresses, one address or two addresses respectively.
The argument text consists of one or more lines. Each
embedded newline in the text must be preceded by a
backslash. Other backslashes in text are treated like the backslashes in the
replacement string of an s editing command; you can use them
to protect initial blanks against the stripping
that's done on every script line.
The r and w editing commands take an optional
rfile (or wfile) parameter,
separated from the command letter by zero or more blanks.
The arguments rfile or wfile
terminate the command line. Each wfile is created
before processing begins. There can be at most ten distinct
wfile arguments in the script.
The b, r, s,t, w,
y, !, and : editing commands take additional
arguments. The following synopses indicate which arguments are separated from
the commands by blanks:
- [2addr] { command_list
}
- Execute command_list only when the pattern space
is selected. (Note that the trailing } must be
the first non-blank character in the line.)
- [1addr]a\
text
- Write text to the standard output after the
pattern space is written.
- [2addr]b label
- Branch to the : (colon) command bearing the label.
If label is empty, branch to the end of the script.
- [2addr]c\
text
- Delete the pattern space. With 0 or 1 address or at the end of a
2-address range, place text on the output.
- [2addr]d
- Delete the pattern space and start the next cycle.
- [2addr]D
- Delete the initial segment of the pattern space through the first
newline and start the next cycle.
- [2addr]g
- Replace the contents of the pattern space by the contents of the hold
space.
- [2addr]G
- Append the contents of the hold space to the pattern space.
- [2addr]h
- Replace the contents of the hold space by the contents of the pattern
space.
- [2addr]H
- Append the contents of the pattern space to the hold space.
- [1addr]i\
text
- Write text to the standard output before the
pattern space is written.
- [2addr]l
- List the pattern space on the standard output in an unambiguous form.
Nonprinting characters are listed as hexadecimal digit pairs, with a
preceding backslash, with the following exceptions:
Character |
Listed as
|
alert |
\a
|
backslash |
\\
|
backspace |
\b
|
carriage return |
\r
|
form-feed |
\f
|
newline |
\n
|
tab |
\t
|
vertical tab |
\v
|
Long lines are folded; the length at which folding occurs is unspecified,
but should be appropriate for the output device.
- [2addr]n
- Copy the pattern space to the standard output and replace the pattern
space with the next line of input.
- [2addr]N
- Append the next line of input to the pattern space, using an embedded
newline to separate the appended material
from the original material. Note that the current line number changes.
- [2addr]p
- Copy (print) the pattern space to the standard output.
- [2addr]P
- Copy (print) the pattern space, up to the first newline,
to the standard output.
- [1addr]q
- Branch to the end of the script and quit without starting a new cycle.
- [1addr]r rfile
- Read the contents of the rfile file. The contents
are placed on the output before reading the next input line.
- [2addr]s/regular expression/replacement string/flags
- Substitute the replacement string for instances
of regular expression in the pattern space.
You can use any character instead of /. The value of
flags is zero or more of:
- n
- n=1 to 512. Substitute for the
nth occurrence only of the
regular expression found within the pattern
space.
- g
- Globally substitute for all non-overlapping instances of
the regular expression rather than just the first
one. If both g and n are specified, g
takes precedence.
- p
- Print the pattern space if a replacement was made.
- w wfile
- Append (write) the pattern space to wfile
if a replacement was made.
- [2addr]t label
- Test; branch to the : (colon) 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.
- [2addr]w wfile
- Append (write) the pattern space to wfile.
- [2addr]x
- Exchange the contents of the pattern and hold spaces.
- [2addr]y/string1/string2/
- Replace all occurrences of collating elements in
string1 with the corresponding collating element
in string2. The lengths of
string1 and string2 should
be equal.
- [2addr]! function
- Apply the function (or command list, if
function is {) only to the lines that
aren't selected by the addresses.
- [0addr]:label
- This command does nothing; it bears a label for
the b and t commands to branch to.
- [1addr]=
- Place the current line number on the standard output as a line with its
own line number.
- [0addr]
- An empty command; ignored.
- [0addr]#
- If a # appears as the first character on any line of a script
file, that entire line is ignored (treated as a comment), with the single
exception that if the first line of the script file begins with
#n, the default output is suppressed (as when the
-n option is specified on the command line).
In the file myfile, find and output only those lines
containing the string “tom”:
sed -n -e "/tom/p" myfile
In the file myfile, replace all occurrences of the string
beneath with the string below, and output
to the file newfile:
sed -e "s/beneath/below/" myfile >newfile
All files are text files. The script_files named by the
-f option consist of editing commands, one per line. Any
number of additional text input files may be specified by the r
command for insertion of unedited data to the standard
output at points predetermined by editing rules. A maximum of 10 additional
output files may be specified through the use of the w command
in the script.
- 0
- Successful completion.
- >0
- An error occurred.
If one or more of the input files (this doesn't include script files)
can't be opened for reading, sed continues to process
the remaining files.
GNU
gawk,
python
Dale Dougherty, sed & awk, O'Reilly and
Associates, 1990.
Brian W. Kernighan and Rob Pike, The UNIX Programming
Environment, Prentice-Hall, 1984.
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