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S2P(1) Perl Programmers Reference Guide S2P(1)
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 AT 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.
perl v5.16.3 2021-02-02 S2P(1)
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On Apache
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