SED(1) OpenBSD Reference Manual SED(1)NAMEsed - stream editor
SYNOPSISsed [-aEnru] command [file ...]
sed [-aEnru] [-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
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' 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 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.
-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
setbuf(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.
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 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
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:
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 should be preceded by a backslash unless it is
a slash. 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 regular
expression is ``abcxdef''.
2. 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''.
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 whitespace. 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 whitespace 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 or followed by whitespace. The function can be
preceded by whitespace as well. The terminating `}' must be preceded by
a newline or optional whitespace.
[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 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 flags in the substitute function is zero or more
of the following:
0 ... 9
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
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.
EXIT STATUS
The sed utility exits 0 on success, and >0 if an error occurs.
SEE ALSOawk(1), ed(1), grep(1), regex(3), setbuf(3), re_format(7)STANDARDS
The sed utility is compliant with the IEEE Std 1003.1-2008 (``POSIX'')
specification.
The flags [-aEru] 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.
HISTORY
A sed command appeared in Version 7 AT&T UNIX.
CAVEATS
The use of semicolons to separate multiple commands is not permitted for
the following commands: a, b, c, i, r, t, w, :, and #.
OpenBSD 4.9 September 3, 2010 OpenBSD 4.9
