SED(1) BSD General Commands Manual SED(1)
NAME
sed -- stream editor
SYNOPSIS
sed [-Ealn] command [file ...]
sed [-Ealn] [-e command] [-f command_file] [-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 regu-lar regular
lar expressions (BRE's). The re_format(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 edit-ing editing
ing 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.
-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.
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, append-ing appending
ing 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 be a number (that counts input lines cumulatively
across input files), a dollar (``$'') character that addresses the last line of input, or a context
address (which consists of a regular expression preceded and followed by a delimiter).
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. 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 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. Also, putting a backslash character before the delimiting
character 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 reg-ular regular
ular 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 func-tion function
tion letter by white space. Each file given as an argument to sed is created (or its contents trun-cated) truncated)
cated) before any input processing begins.
The ``b'', ``r'', ``s'', ``t'', ``w'', ``y'', ``!'', and ``:'' functions all accept additional argu-ments. arguments.
ments. 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 pre-ceded preceded
ceded 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 sep-arate separate
arate 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 condition
dition is set.
[2addr]s/regular expression/replacement/flags
Substitute the replacement string for the first instance of the regular expression in the pat-tern pattern
tern 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 charac-ter character
ter 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.
[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 speci-fied, specified,
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 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 an
``n'' is replaced by a newline character. A pair of backslashes is replaced by a literal back-slash. backslash.
slash. Finally, a backslash followed by any other character (except a newline) is that literal
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 sup-pressed. suppressed.
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(7).
EXIT STATUS
The sed utility exits 0 on success, and >0 if an error occurs.
LEGACY DESCRIPTION
Warnings are not generated for unused labels. In legacy mode, they are.
In the -y function, doubled backslashes are not converted to single ones. In legacy mode, they are.
For more information about legacy mode, see compat(5).
SEE ALSO
awk(1), ed(1), grep(1), regex(3), compat(5), re_format(7)
STANDARDS
The sed utility is expected to be a superset of the IEEE Std 1003.2 (``POSIX.2'') specification.
The -E, -a and -i options are non-standard FreeBSD extensions and may not be available on other operat-ing operating
ing 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 can-not cannot
not be used as delimiters with the ``s'' and ``y'' commands.
BSD May 10, 2005 BSD
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