SED(1) User Commands SED(1)

NAME

sed - stream editor

SYNOPSIS

sed [-Ealnr] command [file ...]
sed [-Ealnr] [-e command] [-f command_file] [-I extension] [-i extension]
[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
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 with the specified extension.
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
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.

Sed Addresses
An address is not required, but if specified must have one of the
following formats:

+o a number that counts input lines cumulatively across input files
(or in each file independently if a -i option is in effect);

+o a dollar (``$'') character that addresses the last line of input
(or the last line of the current file if a -i option was
specified);

+o 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.

Sed Regular Expressions
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''.

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 ``:'' 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.

ENVIRONMENT

The COLUMNS,LANG,LC_ALL,LC_CTYPE and LC_COLLATE environment variables
affect the execution of sed as described in environ(7).

EXIT STATUS

The sed utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

awk(1), ed(1), grep(1), regex(7)

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.

August 21, 2020 SED(1)