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
Page 1 Plan 9 (printed 11/17/24)
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)
Page 2 Plan 9 (printed 11/17/24)