NAME¶
psed - a stream editor
SYNOPSIS¶
psed [-an] script [file ...]
psed [-an] [-e script] [-f script-file] [file ...]
s2p [-an] [-e script] [-f script-file]
DESCRIPTION¶
A stream editor reads the input stream consisting of the specified files (or
standard input, if none are given), processes is line by line by applying a
script consisting of edit commands, and writes resulting lines to standard
output. The filename `"-"' may be used to read standard input.
The edit script is composed from arguments of
-e options and
script-files, in the given order. A single script argument may be specified as
the first parameter.
If this program is invoked with the name
s2p, it will act as a
sed-to-Perl translator. See "sed Script Translation".
sed returns an exit code of 0 on success or >0 if an error occurred.
OPTIONS¶
- -a
- A file specified as argument to the w edit command
is by default opened before input processing starts. Using -a,
opening of such files is delayed until the first line is actually written
to the file.
- -e script
- The editing commands defined by script are appended
to the script. Multiple commands must be separated by newlines.
- -f script-file
- Editing commands from the specified script-file are
read and appended to the script.
- -n
- By default, a line is written to standard output after the
editing script has been applied to it. The -n option suppresses
automatic printing.
COMMANDS¶
sed command syntax is defined as
[
address[
,address]][
!]
function[
argument]
with whitespace being permitted before or after addresses, and between the
function character and the argument. The
addresses and the address
inverter ("!") are used to restrict the application of a command to
the selected line(s) of input.
Each command must be on a line of its own, except where noted in the synopses
below.
The edit cycle performed on each input line consist of reading the line (without
its trailing newline character) into the
pattern space, applying the
applicable commands of the edit script, writing the final contents of the
pattern space and a newline to the standard output. A
hold space is
provided for saving the contents of the pattern space for later use.
Addresses¶
A sed address is either a line number or a pattern, which may be combined
arbitrarily to construct ranges. Lines are numbered across all input files.
Any address may be followed by an exclamation mark (`"!"'), selecting
all lines not matching that address.
- number
- The line with the given number is selected.
- $
- A dollar sign ("$") is the line number of the
last line of the input stream.
- /regular expression/
- A pattern address is a basic regular expression (see
"Basic Regular Expressions"), between the delimiting character
"/". Any other character except "\" or newline may be
used to delimit a pattern address when the initial delimiter is prefixed
with a backslash (`"\"').
If no address is given, the command selects every line.
If one address is given, it selects the line (or lines) matching the address.
Two addresses select a range that begins whenever the first address matches, and
ends (including that line) when the second address matches. If the first
(second) address is a matching pattern, the second address is not applied to
the very same line to determine the end of the range. Likewise, if the second
address is a matching pattern, the first address is not applied to the very
same line to determine the begin of another range. If both addresses are line
numbers, and the second line number is less than the first line number, then
only the first line is selected.
Functions¶
The maximum permitted number of addresses is indicated with each function
synopsis below.
The argument
text consists of one or more lines following the command.
Embedded newlines in
text must be preceded with a backslash. Other
backslashes in
text are deleted and the following character is taken
literally.
- [1addr]a\ text
- Write text (which must start on the line following
the command) to standard output immediately before reading the next line
of input, either by executing the N function or by beginning a new
cycle.
- [2addr]b [label]
- Branch to the : function with the specified
label. If no label is given, branch to the end of the script.
- [2addr]c\ text
- The line, or range of lines, selected by the address is
deleted. The text (which must start on the line following the
command) is written to standard output. With an address range, this occurs
at the end of the range.
- [2addr]d
- Deletes the pattern space and starts the next cycle.
- [2addr]D
- Deletes the pattern space through the first embedded
newline or to the end. If the pattern space becomes empty, a new cycle is
started, otherwise execution of the script is restarted.
- [2addr]g
- Replace the contents of the pattern space with the hold
space.
- [2addr]G
- Append a newline and the contents of the hold space to the
pattern space.
- [2addr]h
- Replace the contents of the hold space with the pattern
space.
- [2addr]H
- Append a newline and the contents of the pattern space to
the hold space.
- [1addr]i\ text
- Write the text (which must start on the line
following the command) to standard output.
- [2addr]l
- Print the contents of the pattern space: non-printable
characters are shown in C-style escaped form; long lines are split and
have a trailing `"\"' at the point of the split; the true end of
a line is marked with a `"$"'. Escapes are: `\a', `\t', `\n',
`\f', `\r', `\e' for BEL, HT, LF, FF, CR, ESC, respectively, and `\'
followed by a three-digit octal number for all other non-printable
characters.
- [2addr]n
- If automatic printing is enabled, write the pattern space
to the standard output. Replace the pattern space with the next line of
input. If there is no more input, processing is terminated.
- [2addr]N
- Append a newline and the next line of input to the pattern
space. If there is no more input, processing is terminated.
- [2addr]p
- Print the pattern space to the standard output. (Use the
-n option to suppress automatic printing at the end of a cycle if
you want to avoid double printing of lines.)
- [2addr]P
- Prints the pattern space through the first embedded newline
or to the end.
- [1addr]q
- Branch to the end of the script and quit without starting a
new cycle.
- [1addr]r file
- Copy the contents of the file to standard output
immediately before the next attempt to read a line of input. Any error
encountered while reading file is silently ignored.
- [2addr]s/regular
expression/replacement /flags
- Substitute the replacement string for the first
substring in the pattern space that matches the regular expression.
Any character other than backslash or newline can be used instead of a
slash to delimit the regular expression and the replacement. To use the
delimiter as a literal character within the regular expression and the
replacement, precede the character by a backslash (`"\"').
Literal newlines may be embedded in the replacement string by preceding a
newline with a backslash.
Within the replacement, an ampersand (`"&"') is replaced by
the string matching the regular expression. The strings `"\1"'
through `"\9"' are replaced by the corresponding subpattern (see
"Basic Regular Expressions"). To get a literal
`"&"' or `"\"' in the replacement text, precede it
by a backslash.
The following flags modify the behaviour of the s
command:
- g
- The replacement is performed for all matching,
non-overlapping substrings of the pattern space.
- 1..9
- Replace only the n-th matching substring of the pattern
space.
- p
- If the substitution was made, print the new value of the
pattern space.
- w file
- If the substitution was made, write the new value of the
pattern space to the specified file.
- [2addr]t [label]
- Branch to the : function with the specified
label if any s substitutions have been made since the most
recent reading of an input line or execution of a t function. If no
label is given, branch to the end of the script.
- [2addr]w file
- The contents of the pattern space are written to the
file.
- [2addr]x
- Swap the contents of the pattern space and the hold
space.
- [2addr]y/string1/string2/
- In the pattern space, replace all characters occurring in
string1 by the character at the corresponding position in
string2. It is possible to use any character (other than a
backslash or newline) 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.
- [1addr]=
- Prints the current line number on the standard output.
- [0addr]: [label]
- The command specifies the position of the label. It
has no other effect.
- [2addr]{ [command]
- [0addr]}
- These two commands begin and end a command list. The first
command may be given on the same line as the opening { command. The
commands within the list are jointly selected by the address(es) given on
the { command (but may still have individual addresses).
- [0addr]# [comment]
- The entire line is ignored (treated as a comment). If,
however, the first two characters in the script are `"#n"',
automatic printing of output is suppressed, as if the -n option
were given on the command line.
BASIC REGULAR EXPRESSIONS¶
A
Basic Regular Expression (BRE), as defined in POSIX 1003.2, consists of
atoms, for matching parts of a string, and
bounds, specifying
repetitions of a preceding atom.
Atoms¶
The possible atoms of a BRE are:
., matching any single character;
^ and
$, matching the null string at the beginning or end of a
string, respectively; a
bracket expressions, enclosed in
[ and
] (see below); and any single character with no other significance
(matching that character). A
\ before one of:
.,
^,
$,
[,
*,
\, matching the character after the
backslash. A sequence of atoms enclosed in
\( and
\) becomes an
atom and establishes the target for a
backreference, consisting of the
substring that actually matches the enclosed atoms. Finally,
\ followed
by one of the digits
0 through
9 is a backreference.
A
^ that is not first, or a
$ that is not last does not have a
special significance and need not be preceded by a backslash to become
literal. The same is true for a
], that does not terminate a bracket
expression.
An unescaped backslash cannot be last in a BRE.
Bounds¶
The BRE bounds are:
*, specifying 0 or more matches of the preceding
atom;
\{count\}, specifying that many repetitions;
\{ minimum,\}, giving a lower limit; and
\{minimum ,maximum\} finally defines a
lower and upper bound.
A bound appearing as the first item in a BRE is taken literally.
Bracket Expressions¶
A
bracket expression is a list of characters, character ranges and
character classes enclosed in
[ and
] and matches any single
character from the represented set of characters.
A character range is written as two characters separated by
- and
represents all characters (according to the character collating sequence) that
are not less than the first and not greater than the second. (Ranges are very
collating-sequence-dependent, and portable programs should avoid relying on
them.)
A character class is one of the class names
alnum digit punct
alpha graph space
blank lower upper
cntrl print xdigit
enclosed in
[: and
:] and represents the set of characters as
defined in
ctype(3).
If the first character after
[ is
^, the sense of matching is
inverted.
To include a literal `"^"', place it anywhere else but first. To
include a literal '"]"' place it first or immediately after an
initial
^. To include a literal `"-"' make it the first (or
second after
^) or last character, or the second endpoint of a range.
The special bracket expression constructs "[[:<:]]" and
"[[:>:]]" match the null string at the beginning and end of a
word respectively. (Note that neither is identical to Perl's `\b' atom.)
Additional Atoms¶
Since some sed implementations provide additional regular expression atoms (not
defined in POSIX 1003.2),
psed is capable of translating the following
backslash escapes:
- \< This is the same as
"[[:>:]]".
- \> This is the same as
"[[:<:]]".
- \w This is an abbreviation for
"[[:alnum:]_]".
- \W This is an abbreviation for
"[^[:alnum:]_]".
- \y Match the empty string at a word boundary.
- \B Match the empty string between any two either
word or non-word characters.
To enable this feature, the environment variable PSEDEXTBRE must be set to a
string containing the requested characters, e.g.:
"PSEDEXTBRE='<>wW'".
ENVIRONMENT¶
The environment variable "PSEDEXTBRE" may be set to extend BREs. See
"Additional Atoms".
DIAGNOSTICS¶
- ambiguous translation for character `%s' in `y'
command
- The indicated character appears twice, with different
translations.
- `[' cannot be last in pattern
- A `[' in a BRE indicates the beginning of a bracket
expression.
- `\' cannot be last in pattern
- A `\' in a BRE is used to make the subsequent character
literal.
- `\' cannot be last in substitution
- A `\' in a substitution string is used to make the
subsequent character literal.
- conflicting flags `%s'
- In an s command, either the `g' flag and an n-th
occurrence flag, or multiple n-th occurrence flags are specified. Note
that only the digits `1' through `9' are permitted.
- duplicate label %s (first defined at %s)
- excess address(es)
- The command has more than the permitted number of
addresses.
- extra characters after command (%s)
- illegal option `%s'
- improper delimiter in s command
- The BRE and substitution may not be delimited with `\' or
newline.
- invalid address after `,'
- invalid backreference (%s)
- The specified backreference number exceeds the number of
backreferences in the BRE.
- invalid repeat clause `\{%s\}'
- The repeat clause does not contain a valid integer value,
or pair of values.
- malformed regex, 1st address
- malformed regex, 2nd address
- malformed regular expression
- malformed substitution expression
- malformed `y' command argument
- The first or second string of a y command is
syntactically incorrect.
- maximum less than minimum in `\{%s\}'
- no script command given
- There must be at least one -e or one -f
option specifying a script or script file.
- `\' not valid as delimiter in `y' command
- option -e requires an argument
- option -f requires an argument
- `s' command requires argument
- start of unterminated `{'
- string lengths in `y' command differ
- The translation table strings in a y command must
have equal lengths.
- undefined label `%s'
- unexpected `}'
- A } command without a preceding { command was
encountered.
- unexpected end of script
- The end of the script was reached although a text line
after a a, c or i command indicated another
line.
- unknown command `%s'
- unterminated `['
- A BRE contains an unterminated bracket expression.
- unterminated `\('
- A BRE contains an unterminated backreference.
- `\{' without closing `\}'
- A BRE contains an unterminated bounds specification.
- `\)' without preceding `\('
- `y' command requires argument
EXAMPLE¶
The basic material for the preceding section was generated by running the sed
script
#no autoprint
s/^.*Warn( *"\([^"]*\)".*$/\1/
t process
b
:process
s/$!/%s/g
s/$[_[:alnum:]]\{1,\}/%s/g
s/\\\\/\\/g
s/^/=item /
p
on the program's own text, and piping the output into "sort -u".
SED SCRIPT TRANSLATION¶
If this program is invoked with the name
s2p it will act as a sed-to-Perl
translator. After option processing (all other arguments are ignored), a Perl
program is printed on standard output, which will process the input stream (as
read from all arguments) in the way defined by the sed script and the option
setting used for the translation.
SEE ALSO¶
perl(1),
re_format(7)
BUGS¶
The
l command will show escape characters (ESC) as `"\e"', but
a vertical tab (VT) in octal.
Trailing spaces are truncated from labels in
:,
t and
b
commands.
The meaning of an empty regular expression (`"//"'), as defined by
sed, is "the last pattern used, at run time". This deviates
from the Perl interpretation, which will re-use the "last last
successfully executed regular expression". Since keeping track of pattern
usage would create terribly cluttered code, and differences would only appear
in obscure context (where other
sed implementations appear to deviate,
too), the Perl semantics was adopted. Note that common usage of this feature,
such as in "/abc/s//xyz/", will work as expected.
Collating elements (of bracket expressions in BREs) are not implemented.
STANDARDS¶
This
sed implementation conforms to the IEEE Std1003.2-1992
("POSIX.2") definition of
sed, and is compatible with the
OpenBSD implementation, except where otherwise noted (see
"BUGS").
AUTHOR¶
This Perl implementation of
sed was written by Wolfgang Laun,
Wolfgang.Laun@alcatel.at.
COPYRIGHT and LICENSE¶
This program is free and open software. You may use, modify, distribute, and
sell this program (and any modified variants) in any way you wish, provided
you do not restrict others from doing the same.