sed [-Ealnr] command [file ...]
sed [-Ealnr] [-e command] [-f
command_file] [-I[extension] |
-i[extension]] [file ...]
The sed utility reads the specified files, or the standard
input if no files are specified, modifying the input as specified by a list
of commands. The input is then written to the standard output.
A single command may be specified as the first argument to
sed. Multiple commands may be specified by using the -e or
-f options. All commands are applied to the input in the order they
are specified regardless of their origin.
The following options are available:
- -E
- Interpret regular expressions as extended (modern) regular expressions
rather than basic regular expressions (BRE's). The regex(7) manual
page fully describes both formats.
- -a
- The files listed as parameters for the ``w'' functions are created (or
truncated) before any processing begins, by default. The -a option
causes sed to delay opening each file until a command containing
the related ``w'' function is applied to a line of input.
- -e command
- Append the editing commands specified by the command argument to
the list of commands.
- -f
command_file
- Append the editing commands found in the file command_file to the
list of commands. The editing commands should each be listed on a separate
line.
- -I[extension]
- Edit files in-place, saving backups if extension was specified. It
is not recommended to omit saving backups when in-place editing files, as
you risk corruption or partial content in situations where disk space is
exhausted, etc.
Note that in-place editing with -I still takes place in
a single continuous line address space covering all files, although each
file preserves its individuality instead of forming one output stream.
The line counter is never reset between files, address ranges can span
file boundaries, and the ``$'' address matches only the last line of the
last file. (See Sed Addresses . ) That can lead to unexpected
results in many cases of in-place editing, where using -i is
desired.
- -i[extension]
- Edit files in-place similarly to -I, but treat each file
independently from other files. In particular, line numbers in each file
start at 1, the ``$'' address matches the last line of the current file,
and address ranges are limited to the current file. (See Sed Addresses
. ) The net result is as though each file were edited by a separate
sed instance.
- -l
- Make output line buffered.
- -n
- By default, each line of input is echoed to the standard output after all
of the commands have been applied to it. The -n option suppresses
this behavior.
- -r
- Same as -E for compatibility with GNU sed.
The form of a sed command is as follows:
[address[,address]]function[arguments]
Whitespace may be inserted before the first address and the
function portions of the command.
Normally, sed cyclically copies a line of input, not
including its terminating newline character, into a pattern space,
(unless there is something left after a ``D'' function), applies all of the
commands with addresses that select that pattern space, copies the pattern
space to the standard output, appending a newline, and deletes the pattern
space.
Some of the functions use a hold space to save all or part
of the pattern space for subsequent retrieval.
If an input file is growing while sed is running, the ``$''
address match may be unreliable.
An address is not required, but if specified must have one of the
following formats:
- a number that counts input lines cumulatively across input files (or in
each file independently if a -i option is in effect);
- a dollar (``$'') character that addresses the last line of input (or the
last line of the current file if a -i option was specified);
- a context address that consists of a regular expression preceded and
followed by a delimiter. The closing delimiter can also optionally be
followed by the ``I'' character, to indicate that the regular expression
is to be matched in a case-insensitive way.
A command line with no addresses selects every pattern
space.
A command line with one address selects all of the pattern
spaces that match the address.
A command line with two addresses selects an inclusive range.
This range starts with the first pattern space that matches the first
address. The end of the range is the next following pattern space that
matches the second address. If the second address is a number less than
or equal to the line number first selected, only that line is selected.
The number in the second address may be prefixed with a (``+'') to
specify the number of lines to match after the first pattern. In the
case when the second address is a context address, sed does not
re-match the second address against the pattern space that matched the
first address. Starting at the first line following the selected range,
sed starts looking again for the first address.
Editing commands can be applied to non-selected pattern spaces
by use of the exclamation character (``!'') function.
The regular expressions used in , by default, are basic
regular expressions (BREs, see regex(7) for more information), but
extended (modern) regular expressions can be used instead if the -E
flag is given. In addition, sed has the following two additions to
regular expressions:
- 1.
- In a context address, any character other than a backslash (``\'') or
newline character may be used to delimit the regular expression. The
opening delimiter needs to be preceded by a backslash unless it is a
slash. For example, the context address \xabcx is equivalent to /abc/ .
Also, putting a backslash character before the delimiting character within
the regular expression causes the character to be treated literally. For
example, in the context address \xabc\xdefx , the RE delimiter is an ``x''
and the second ``x'' stands for itself, so that the regular expression is
``abcxdef''.
- 2.
- The escape sequence \n matches a newline character embedded in the pattern
space. You cannot, however, use a literal newline character in an address
or in the substitute command.
One special feature of sed regular expressions is that
they can default to the last regular expression used. If a regular
expression is empty, i.e., just the delimiter characters are specified,
the last regular expression encountered is used instead. The last
regular expression is defined as the last regular expression used as
part of an address or substitute command, and at run-time, not
compile-time. For example, the command ``/abc/s//XXX/'' will substitute
``XXX'' for the pattern ``abc''.
In the following list of commands, the maximum number of
permissible addresses for each command is indicated by [0addr], [1addr], or
[2addr], representing zero, one, or two addresses.
The argument text consists of one or more lines. To embed a
newline in the text, precede it with a backslash. Other backslashes in text
are deleted and the following character taken literally.
The ``r'' and ``w'' functions take an optional file parameter,
which should be separated from the function letter by white space. Each file
given as an argument to sed is created (or its contents truncated)
before any input processing begins.
The ``b'', ``r'', ``s'', ``t'', ``w'', ``y'', ``!'', and ``:''
functions all accept additional arguments. The following synopses indicate
which arguments have to be separated from the function letters by white
space characters.
Two of the functions take a function-list. This is a list of
sed functions separated by newlines, as follows:
{ function
function
...
function
}
The ``{'' can be preceded by white space and can be followed by
white space. The function can be preceded by white space. The terminating
``}'' must be preceded by a newline or optional white space.
- [2addr] function-list
- Execute function-list only when the pattern space is selected.
- [1addr]a\
- text
- Write text to standard output immediately before each attempt to
read a line of input, whether by executing the ``N'' function or by
beginning a new cycle.
- [2addr]b[label]
- Branch to the ``:'' function with the specified label. If the label is not
specified, 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, text is written to the standard 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
character and start the next cycle.
- [2addr]g
- Replace the contents of the pattern space with the contents of the hold
space.
- [2addr]G
- Append a newline character followed by the contents of the hold space to
the pattern space.
- [2addr]h
- Replace the contents of the hold space with the contents of the pattern
space.
- [2addr]H
- Append a newline character followed by the contents of the pattern space
to the hold space.
- [1addr]i\
- text
- Write text to the standard output.
- [2addr]l
- (The letter ell.) Write the pattern space to the standard output in a
visually unambiguous form. This form is as follows:
- backslash
- \\
- alert
- \a
- form-feed
- \f
- carriage-return
- \r
- tab
- \t
- vertical tab
- \v
Nonprintable characters are written as three-digit octal
numbers (with a preceding backslash) for each byte in the character
(most significant byte first). Long lines are folded, with the point of
folding indicated by displaying a backslash followed by a newline. The
end of each line is marked with a ``$''.
- [2addr]n
- Write the pattern space to the standard output if the default output has
not been suppressed, 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 character to separate the appended material from the original
contents. Note that the current line number changes.
- [2addr]p
- Write the pattern space to standard output.
- [2addr]P
- Write the pattern space, up to the first newline character to the standard
output.
- [1addr]q
- Branch to the end of the script and quit without starting a new cycle.
- [1addr]r file
- Copy the contents of file to the standard output immediately before
the next attempt to read a line of input. If file cannot be read
for any reason, it is silently ignored and no error condition is set.
- [2addr]s/regular expression/replacement/flags
- Substitute the replacement string for the first instance of the regular
expression in the pattern space. Any character other than backslash or
newline can be used instead of a slash to delimit the RE and the
replacement. Within the RE and the replacement, the RE delimiter itself
can be used as a literal character if it is preceded by a backslash.
An ampersand (``&'') appearing in the replacement is
replaced by the string matching the RE. The special meaning of ``&''
in this context can be suppressed by preceding it by a backslash. The
string ``\#'', where ``#'' is a digit, is replaced by the text matched
by the corresponding backreference expression (see regex(7))
.
A line can be split by substituting a newline character into
it. To specify a newline character in the replacement string, precede it
with a backslash.
The value of flags in the substitute function is zero
or more of the following:
- N
- Make the substitution only for the N'th occurrence of the regular
expression in the pattern space.
- g
- Make the substitution for all non-overlapping matches of the regular
expression, not just the first one.
- p
- Write the pattern space to standard output if a replacement was made. If
the replacement string is identical to that which it replaces, it is still
considered to have been a replacement.
- w file
- Append the pattern space to file if a replacement was made. If the
replacement string is identical to that which it replaces, it is still
considered to have been a replacement.
- I
- Match the regular expression in a case-insensitive way.
- [2addr]t [label]
- Branch to the ``:'' function bearing the label if any substitutions have
been made since the most recent reading of an input line or execution of a
``t'' function. If no label is specified, branch to the end of the script.
- [2addr]w file
- Append the pattern space to the file.
- [2addr]x
- Swap the contents of the pattern and hold spaces.
- [2addr]y/string1/string2/
- Replace all occurrences of characters in string1 in the pattern
space with the corresponding characters from string2. Any character
other than a backslash or newline can be used instead of a slash to
delimit the strings. Within string1 and string2, a backslash
followed by any character other than a newline is that literal character,
and a backslash followed by an ``n'' is replaced by a newline character.
- [2addr]!function
- [2addr]!function-list
- Apply the function or function-list only to the lines that are not
selected by the address(es).
- [0addr]:label
- This function does nothing; it bears a label to which the ``b'' and ``t''
commands may branch.
- [1addr]=
- Write the line number to the standard output followed by a newline
character.
- [0addr]
- Empty lines are ignored.
- [0addr]#
- The ``#'' and the remainder of the line are ignored (treated as a
comment), with the single exception that if the first two characters in
the file are ``#n'', the default output is suppressed. This is the same as
specifying the -n option on the command line.
The COLUMNS,LANG,LC_ALL,LC_CTYPE and
LC_COLLATE environment variables affect the execution of sed
as described in environ(7).
The sed utility exits 0 on success, and >0 if an error
occurs.
The sed utility is expected to be a superset of the IEEE
Std 1003.2 (``POSIX.2'') specification.
The -E, I , a and -i options, the prefixing ``+'' in
the second member of an address range, as well as the ``I'' flag to the
address regular expression and substitution command are non-standard
extensions and may not be available on other operating systems.
A sed command, written by L. E. McMahon, appeared in
Version 7 AT&T UNIX.
"Diomidis D. Spinellis" <dds@FreeBSD.org>
Multibyte characters containing a byte with value 0x5C (ASCII `\')
may be incorrectly treated as line continuation characters in arguments to
the ``a'', ``c'' and ``i'' commands. Multibyte characters cannot be used as
delimiters with the ``s'' and ``y'' commands.