sed —
stream editor
sed |
[ -aEnru
]
[]
command
[file ... ] |
sed |
[ -aEnru
]
[-e
command
]
[-f
command_file
]
[]
[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
separated by newlines or semicolons, or 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 options are as follows:
-
-
-a- The files listed as parameters for the
w function or flag 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 or flag is applied to a line of input.
-
-
-E- Interpret regular expressions using POSIX extended regular expression
syntax. The default behaviour is to use POSIX basic regular expression
syntax.
-
-
-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
it risks corruption or partial content in situations where disk space is
exhausted, etc.
-
-
-r- An alias for
-E, for compatibility with
GNU sed.
-
-
-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.
-
-
-u- Force output to be line buffered, printing each line as it becomes
available. By default, output is line buffered when standard output is a
terminal and block buffered otherwise. See
setvbuf(3) for a more
detailed explanation.
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.
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 is a regular expression preceded and
followed by a delimiter. The delimiter can be any character except a newline
or a backslash. Unless it is a slash, the opening delimiter needs to be
escaped with a backslash.
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 the inclusive range from the first
pattern space that matches the first address through the next pattern space
that matches the second. (If the second address is a number less than or equal
to the line number first selected, only that line is selected.) 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.
By default,
sed regular expressions are basic
regular expressions (BREs). Extended regular expressions are supported using
the
-E and
-r options. See
re_format(7) for more
information on regular expressions. In addition,
sed has the following two additions to
BREs:
- The character delimiting the regular expression can be used inside the
regular expression by prepending a backslash or by including it in a
character class. For example, in the context address \x\x[xy]x, the RE
delimiter is an ‘x’ and the other ‘x’
characters stand for themselves, so that the regular expression is
“x[xy]”.
- The escape sequence \n matches a newline character embedded in the pattern
space. You can't, 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, as well as the
w flag to the
s function, take a
file parameter, which should be separated
from the function or flag by whitespace. Files are created (or their contents
truncated) before any input processing begins.
The
b,
r,
s,
t,
w,
y,
and
: functions all accept additional
arguments. The synopses below indicate which arguments have to be separated
from the function letters by whitespace characters.
Functions can be combined to form a
function list,
a list of
sed functions each followed by a
newline, as follows:
{ function
function
...
function
}
The braces can be preceded and followed by whitespace. The functions can be
preceded by whitespace as well.
Functions and function lists may be preceded by an exclamation mark, in which
case they are applied only to lines that are
not
selected by the addresses.
-
-
- [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
- backspace
- \b
- form-feed
- \f
- carriage-return
- \r
- tab
- \t
- vertical tab
- \v
Non-printable 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/RE/replacement/flags
- Substitute the replacement string for the
first instance of the regular expression
RE in the pattern space. Any character
other than backslash or newline can be used instead of a slash to delimit
the regular expression and the replacement. Also see the the section about
SED REGULAR
EXPRESSIONS.
An ampersand (‘
&’) appearing in
the replacement is replaced by the string matching the regular expression.
The string ‘\#’, where
‘#’ is a digit, is replaced by the
text matched by the corresponding backreference expression (see
re_format(7)).
All other instances of a backslash will print the literal character
following it. Using a backslash before any other character other than
‘&’,
‘\’, digit, newline (ascii 0x0a),
and the delimiter is unspecified and might not be portable to other
implementations of sed.
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, where
N is a positive integer starting with
1 ...
9.
-
-
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 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 another
backslash is replaced by a single backslash, a backslash followed by an
‘n’ is replaced by a newline character, and a backslash
followed by the delimiting character is replaced by that character,
causing it to be treated literally, with the exception of the
‘n’ character, which will still be treated like a newline
character. It is an error for a backslash to not be followed by another
backslash, ‘n’, or the delimiting character, or for
string1 to contain repeating
characters.
-
-
- [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.
-
-
COLUMNS- If set to a positive integer, output from the
l function is formatted to the given
width in columns. Otherwise, sed
defaults to the terminal width, or 80 columns if the output is not a
terminal.
The
sed utility exits 0 on success,
and >0 if an error occurs.
awk(1),
ed(1),
grep(1),
re_format(7)
The
sed utility is compliant with the
IEEE Std 1003.1-2008
(“POSIX.1”) specification.
The flags [
-aEiru
] are
extensions to that specification.
The use of newlines to separate multiple commands on the command line is
non-portable; the use of newlines to separate multiple commands within a
command file (
-f
command_file) is portable.
A
sed command appeared in
Version 7 AT&T UNIX.
The use of semicolons to separate multiple commands is not permitted for the
following commands:
a,
b,
c,
i,
r,
t,
w,
:, and
#.
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