Normally sed is invoked like this:
sed SCRIPT INPUTFILE...
The full format for invoking sed is:
sed OPTIONS... [SCRIPT] [INPUTFILE...]
If you do not specify INPUTFILE, or if INPUTFILE is -,
sed filters the contents of the standard input. The script
is actually the first non-option parameter, which sed specially
considers a script and not an input file if (and only if) none of the
other options specifies a script to be executed, that is if neither
of the -e and -f options is specified.
sed may be invoked with the following command-line options:
- Print out the version of sed that is being run and a copyright notice,
- Print a usage message briefly summarizing these command-line options
and the bug-reporting address,
- By default, sed prints out the pattern space
at the end of each cycle through the script (see How
These options disable this automatic printing,
and sed only produces output when explicitly told to
- Add the commands in script to the set of commands to be
run while processing the input.
- Add the commands contained in the file script-file
to the set of commands to be run while processing the input.
- This option specifies that files are to be edited in-place.
GNU sed does this by creating a temporary file and
sending output to this file rather than to the standard
This option implies -s.
When the end of the file is reached, the temporary file is
renamed to the output file's original name. The extension,
if supplied, is used to modify the name of the old file
before renaming the temporary file, thereby making a backup
This rule is followed: if the extension doesn't contain a
then it is appended to the end of the current filename as a
suffix; if the extension does contain one or more
characters, then each asterisk is replaced with the
current filename. This allows you to add a prefix to the
backup file, instead of (or in addition to) a suffix, or
even to place backup copies of the original files into another
directory (provided the directory already exists).
If no extension is supplied, the original file is
overwritten without making a backup.
- Specify the default line-wrap length for the
A length of 0 (zero) means to never wrap long lines. If
not specified, it is taken to be 70.
- GNU sed includes several extensions to POSIX
sed. In order to simplify writing portable scripts, this
option disables all the extensions that this manual documents,
including additional commands.
Most of the extensions accept sed programs that
are outside the syntax mandated by POSIX, but some
of them (such as the behavior of the N command
described in see Reporting Bugs) actually violate the
standard. If you want to disable only the latter kind of
extension, you can set the
to a non-empty value.
- This option is available on every platform, but is only effective where the
operating system makes a distinction between text files and binary files.
When such a distinction is made—as is the case for MS-DOS, Windows,
Cygwin—text files are composed of lines separated by a carriage return
and a line feed character, and sed does not see the
ending CR. When this option is specified, sed will open
input files in binary mode, thus not requesting this special processing
and considering lines to end at a line feed.
- This option is available only on platforms that support
symbolic links and has an effect only if option -i
is specified. In this case, if the file that is specified
on the command line is a symbolic link, sed will
follow the link and edit the ultimate destination of the
link. The default behavior is to break the symbolic link,
so that the link destination will not be modified.
- Use extended regular expressions rather than basic
regular expressions. Extended regexps are those that
egrep accepts; they can be clearer because they
usually have less backslashes, but are a GNU extension
and hence scripts that use them are not portable.
See Extended regular expressions.
- By default, sed will consider the files specified on the
command line as a single continuous long stream. This GNU sed
extension allows the user to consider them as separate files:
range addresses (such as ‘/abc/,/def/’) are not allowed
to span several files, line numbers are relative to the start
of each file,
$ refers to the last line of each file,
and files invoked from the
R commands are rewound at the
start of each file.
- Buffer both input and output as minimally as practical.
(This is particularly useful if the input is coming from
the likes of ‘tail -f’, and you wish to see the transformed
output as soon as possible.)
If no -e, -f, --expression, or --file
options are given on the command-line,
then the first non-option argument on the command line is
taken to be the script to be executed.
If any command-line parameters remain after processing the above,
these parameters are interpreted as the names of input files to
A file name of ‘-’ refers to the standard input stream.
The standard input will be processed if no file names are specified.