SED(1) Commands and Applications SED(1)
NAME
sed - stream editor
SYNOPSIS
sed command [-an] [file ...]
sed [-an] [-e command]... [-f command_file]... [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 sed. Multi‐
ple commands may be specified by using the -e or -f options. All com‐
mands are applied to the input in the order they are specified regard‐
less of their origin.
The following options are available:
-a The files listed as parameters for the w (write) functions are
created (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.
-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 op‐
tion 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 ter‐
minating 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 pat‐
tern 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 ($) char‐
acter that addresses the last line of input, or a context address
(which consists of a regular expression preceded and followed by a de‐
limiter).
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.
Sed Regular Expressions
The sed regular expressions are basic regular expressions (BRE's, see
regex(3) for more information). In addition, sed has the following two
additions to BRE's:
In a context address, any character other than a backslash (\f[R]) or
newline character may be used to delimit the regular expression.
Also, putting a backslash character before the delimiting char‐
acter causes the character to be treated literally. For exam‐
ple, in the context address \xabc\xdefx, the RE delimiter is an
x and the second x stands for itself, so that the regular ex‐
pression is abcxdef.
The escape sequence \n matches a newline character embedded in the pat‐
tern 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 ex‐
pression 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 argu‐
ments. The following synopses indicate which arguments have to be sep‐
arated 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:
-literal -offset indent
{ 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.ft R
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.ft R
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.ft R
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
newline \n
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 indi‐
cated 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 em‐
bedded 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 be‐
fore 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 de‐
limit the RE and the replacement. Within the RE and the re‐
placement, 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 .ft R
where # is a digit, is replaced by the text matched by the cor‐
responding 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 flags in the substitute function is zero or more of the
following:
Make the substitution only for the N'th occurrence of the regu‐
lar expression in the pattern space.
Make the substitution for all non-overlapping matches of the regular
expression, not just the first one.
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.
Append the pattern space to file if a replacement was made. If the re‐
placement 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 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 re‐
placed 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 char‐
acters in the file are #n, the default output is suppressed.
This is the same as specifying the -n option on the command
line.
The sed utility exits 0 on success and >0 if an error occurs.
VERSION
This manual page documents sed version 2.0 for GNO/ME.
SEE ALSO
awk(1), ed(1), grep(1), regex(3), re_format(7)
ATTRIBUTIONS
This command was ported from FreeBSD source code for distribution with
GNO/ME 2.0.6.
HISTORY
An implementation of sed for the Apple IIGS was written in 1990 and
distributed separately from GNO.
STANDARDS
The sed function is expected to be a superset of the POSIX.2 specifica‐
tion.
GNO November 1997 SED(1)
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