SED(1)SED(1)NAMEsed - stream editor
SYNOPSISsed [-Ealnr] command [file ...]
sed [-Ealnr] [-e command] [-f command_file] [-I extension] [-i exten‐
sion] [file ...]
DESCRIPTION
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 com‐
mands. The input is then written to the standard output.
A single command may be specified as the first argument to . 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
re_format(7) manual page fully describes both formats.
-a The files listed as parameters for the ``w'' functions are cre‐
ated (or truncated) before any processing begins, by default.
The -a option causes sed to delay opening each file until a com‐
mand 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 with the specified exten‐
sion. If a zero-length extension is given, no backup will be
saved. It is not recommended to give a zero-length extension
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 ``$'' address matches
only the last line of the last file. (See Sed Addresses . )
That can lead to unexpected results in many cases of in-place
editing, where using -i is desired.
-i extension
Edit files in-place similarly to -I, but treat each file inde‐
pendently from other files. In particular, line numbers in each
file start at 1, the ``$'' 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.
Sed Addresses
An address is not required, but if specified must have one of the fol‐
lowing 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 speci‐
fied);
· 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 spa‐
ces 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 pat‐
tern 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.
Sed Regular Expressions
The regular expressions used in , by default, are basic regular expres‐
sions (BREs, see re_format(7) for more information), but extended (mod‐
ern) regular expressions can be used instead if the -E flag is given.
In addition, sed has the following two additions to regular expres‐
sions:
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 back‐
slash character before the delimiting character within the regu‐
lar expression causes the character to be treated literally.
For example, in the context address \xabc\xdefx , the RE delim‐
iter 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 com‐
mand, and at run-time, not compile-time. For example, the com‐
mand ``/abc/s//XXX/'' will substitute ``XXX'' for the pattern
``abc''.
Sed Functions
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 ``:'' func‐
tions 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 func‐
tions 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 pat‐
tern 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 out‐
put 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 con‐
dition 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
re_format(7)) .
A line can be split by substituting a newline character into it.
To specify a newline character in the replacement string, pre‐
cede 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 regu‐
lar 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 substitu‐
tions have been made since the most recent reading of an input
line or execution of a ``t'' function. If no label is speci‐
fied, 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 char‐
acter 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 new‐
line 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 sup‐
pressed. This is the same as specifying the -n option on the
command line.
ENVIRONMENT
The COLUMNS,LANG,LC_ALL,LC_CTYPE and LC_COLLATE environment variables
affect the execution of sed as described in environ(5).
EXIT STATUS
The sed utility exits 0 on success, and >0 if an error occurs.
SEE ALSOawk(1), ed(1), grep(1), regex(3), re_format(5)STANDARDS
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.
HISTORY
A sed command, written by L. E. McMahon, appeared in Version 7 AT&T
UNIX.
AUTHORS
"Diomidis D. Spinellis" <dds@FreeBSD.org>
BUGS
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.
May 24, 2009 SED(1)
