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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.

       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

       [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.


       [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.)

       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 '{'

           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").