S2P(1) Perl Programmers Reference Guide S2P(1)NAMEpsed - a stream editor
SYNOPSISpsed [-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 out-
put. 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 new-
lines.
-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
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addresses and the address inverter ("!") are used to res-
trict 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 read-
ing 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 pro-
vided 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 ini-
tial 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.
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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 func-
tion 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 follow-
ing 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
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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 pat-
tern 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 new-
line or to the end.
[1addr]q
Branch to the end of the script and quit without start-
ing a new cycle.
[1addr]r file
Copy the contents of the file to standard output immedi-
ately 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 sub-
string in the pattern space that matches the regular
expression. Any character other than backslash or new-
line can be used instead of a slash to delimit the regu-
lar 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
(`"\"').
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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 Expres-
sions"). To get a literal `"&"' or `"\"' in the replace-
ment text, precede it by a backslash.
The following flags modify the behaviour of the s com-
mand:
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.
[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 open-
ing { command. The commands within the list are jointly
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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 begin-
ning or end of a string, respectively; a bracket expres-
sions, enclosed in [ and ] (see below); and any single char-
acter 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.
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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 immedi-
ately 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.
characters.
\B Match the empty string between any two either word or non-
word
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
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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 subsitution string is used to make the subse-
quent 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 syntacti-
cally incorrect.
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maximum less than minimum in `\{%s\}'
no script command given
There must be at least one -e or one -f option specify-
ing 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 commanf must have
equal lengths.
undefined label `%s'
unexpected `}'
A } command without a preceding { command was encoun-
tered.
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
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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 stan-
dard 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 ALSOperl(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 com-
mands.
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 expres-
sion". 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 vari-
ants) in any way you wish, provided you do not restrict oth-
ers from doing the same.
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