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Add documentation for regex import

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Mahmoud Al-Qudsi 2020-11-25 21:55:48 -06:00
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doc_src/cmds/string-match.rst
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@ -27,6 +27,8 @@ If ``--index`` or ``-n`` is given, each match is reported as a 1-based start pos
If ``--regex`` or ``-r`` is given, PATTERN is interpreted as a Perl-compatible regular expression, which does not have to match the entire STRING. For a regular expression containing capturing groups, multiple items will be reported for each match, one for the entire match and one for each capturing group. With this, only the matching part of the STRING will be reported, unless ``--entire`` is given.
When matching via regular expressions, it is possible to directly import matches as fish variables by means of named capture groups using the PCRE2 syntax. This behavior is automatic and occurs in addition to any other match reporting. The default behavior with `--regex` results in the initialization of fish variables in the default scope containing the matched text corresponding to each named capture group. A named capture group matching a zero-length string will be initialized as a fish variable containing a likewise empty string (i.e. the equivalent of `""`), but a named capture group that did not match will result in an empty (null) fish variable. When `--regex` is used in conjunction with `--all`, this behavior changes slightly: for each of the *n* matching sequences, the *n*th index of each named variable will contain the contents of the corresponding named capture group for the *n*th match, but will contain an empty string if the group was empty or if the group did not match.
If ``--invert`` or ``-v`` is used the selected lines will be only those which do not match the given glob pattern or regular expression.
Exit status: 0 if at least one match was found, or 1 otherwise.
@ -104,4 +106,21 @@ Match Regex Examples
>_ string match -r -i '0x[0-9a-f]{1,8}' 'int magic = 0xBadC0de;'
0xBadC0de
>_ echo $version
3.1.2-1575-ga2ff32d90
>_ string match -rq '(?<major>\d+).(?<minor>\d+).(?<revision>\d+)' -- $version
>_ echo "You are using fish $major!"
You are using fish 3!
>_ string match -raq ' *(?<sentence>[^.!?]+)(?<punctuation>[.!?])?' "hello, friend. goodbye"
>_ printf "%s\n" -- $sentence
hello, friend
goodbye
>_ printf "%s\n" -- $punctuation
.
>_ string match -rq '(?<word>hello)' 'hi'
>_ count $word
0
.. END EXAMPLES