SH-REGEX(1)                                           SH-REGEX(1)

     NAME
          re, match - shell script regular expression handling

     SYNOPSIS
          load regex

          match regex [ arg... ]
          ${re op arg... }

     DESCRIPTION
          Regex is a loadable module for sh(1) that provides access to
          regular-expression pattern matching and substitution.  For
          details of regular expression syntax in Inferno, see
          regexp(6). Regex defines one builtin command, match, and one
          builtin substitution operator, re.  Match gives a false exit
          status if its argument regex fails to match any arg. Re pro-
          vides several operations, detailed below:

          ${re g regexp [ arg...]}
                    Yields a list of each arg that matches regexp.

          ${re v regexp [ arg...]}
                    Yields a list of each arg that does not match
                    regexp.

          ${re m regexp arg}
                    Yields the portion of arg that matches regexp, or
                    an empty list if there was no match.

          ${re M regexp arg}
                    Yields a list consisting of the portion of arg
                    that matches regexp, followed by list elements
                    giving the portion of arg that matched each paren-
                    thesized subexpression in turn.

          ${re mg regexp arg}
                    Similar to re m except that it applies the match
                    consecutively through arg, yielding a list of all
                    the portions of arg that match regexp. If a match
                    is made to the null string, no subsequent substi-
                    tutions will take place.

          ${re s regexp subs [ arg... ]}
                    For each arg, re s substitutes the first occur-
                    rence of regexp (if any) by subs. If subs contains
                    a sequence of the form \d where d is a single dec-
                    imal digit, the dth parenthesised subexpression in
                    regexp will be substituted in its place.  \0 is
                    substituted by the entire match.  If any other
                    character follows a backslash (\), that character

     SH-REGEX(1)                                           SH-REGEX(1)

                    will be substituted.  Arguments which contain no
                    match to regexp will be left unchanged.

          ${re sg regexp subs [ arg... ]}
                    Similar to re s except that all matches of regexp
                    within each arg will be substituted for, rather
                    than just the first match. Only one occurrence of
                    the null string is substituted.

     EXAMPLES
          List all files in the current directory that end in .dis or
          .sbl:
               ls -l ${re g '\.(sbl|dis)$' *}

          Break string up into its constituent characters, putting the
          result in shell variable x:
               x = ${re mg '.|\n' string}

          Quote a string s so that it can be used as a literal regular
          expression without worrying about metacharacters:
               s = ${re sg '[*|[\\+.^$()?]' '\\\0' $s}

          Define a substitution function pat2regexp to convert shell-
          style patterns into equivalent regular expressions (e.g.
          ``?.sbl*'' would become ``^.\.sbl.*$''):
               load std
               subfn pat2regexp {
                    result = '^' ^ ${re sg '\*' '.*'
                         ${re sg '?' '.'
                              ${re sg '[()+\\.^$|]' '\\\0' $*}
                         }
                    } ^ '$'
               }

     SOURCE
          /appl/cmd/sh/regex.b

     SEE ALSO
          regexp(6), regex(2), sh(1), string(2), sh-std(1)