SED(1) BSD General Commands Manual SED(1)

NAME

sed -- stream editor

SYNOPSIS

sed [-Ealnr] _c_o_m_m_a_n_d [_f_i_l_e _._._.]

sed [-Ealnr] [-e _c_o_m_m_a_n_d] [-f _c_o_m_m_a_n_d___f_i_l_e] [-I _e_x_t_e_n_s_i_o_n] [-i _e_x_t_e_n_s_i_o_n]

[_f_i_l_e _._._.]

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 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

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 _c_o_m_m_a_n_d

Append the editing commands specified by the _c_o_m_m_a_n_d argument to

the list of commands.

-f _c_o_m_m_a_n_d___f_i_l_e

Append the editing commands found in the file _c_o_m_m_a_n_d___f_i_l_e to the

list of commands. The editing commands should each be listed on

a separate line.

-I _e_x_t_e_n_s_i_o_n

Edit files in-place, saving backups with the specified _e_x_t_e_n_s_i_o_n.

If a zero-length _e_x_t_e_n_s_i_o_n is given, no backup will be saved. It

is not recommended to give a zero-length _e_x_t_e_n_s_i_o_n when in-place

editing files, as you risk corruption or partial content in situ-

ations 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 _S_e_d _A_d_d_r_e_s_s_e_s.) That

can lead to unexpected results in many cases of in-place editing,

where using -i is desired.

-i _e_x_t_e_n_s_i_o_n

Edit files in-place similarly to -I, but treat each file indepen-

dently 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 _S_e_d _A_d_d_r_e_s_s_e_s.) 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 por-

tions of the command.

Normally, sed cyclically copies a line of input, not including its termi-

nating newline character, into a _p_a_t_t_e_r_n _s_p_a_c_e, (unless there is some-

thing 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 _h_o_l_d _s_p_a_c_e 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 follow-

ing 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 pre-

ceded 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-insensi-

tive 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 num-

ber of lines to match after the first pattern. In the case when the sec-

ond address is a context address, sed does not re-match the second

address against the pattern space that matched the first address. Start-

ing 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 sed, by default, are basic regular

expressions (BREs, see re_format(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 sub-

stitute 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 _t_e_x_t 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 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 _t_e_x_t 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, _t_e_x_t 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 _t_e_x_t 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 new-

line. 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 _f_i_l_e to the standard output immediately

before the next attempt to read a line of input. If _f_i_l_e 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, precede

it with a backslash.

The value of _f_l_a_g_s 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 _f_i_l_e Append the pattern space to _f_i_l_e 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 specified,

branch to the end of the script.

[2addr]w _f_i_l_e

Append the pattern space to the _f_i_l_e.

[2addr]x

Swap the contents of the pattern and hold spaces.

[2addr]y/string1/string2/

Replace all occurrences of characters in _s_t_r_i_n_g_1 in the pattern

space with the corresponding characters from _s_t_r_i_n_g_2. Any char-

acter other than a backslash or newline can be used instead of a

slash to delimit the strings. Within _s_t_r_i_n_g_1 and _s_t_r_i_n_g_2, 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

_n_o_t 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 charac-

ters 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(3), re_format(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 FreeBSD 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.

BSD May 24, 2009 BSD