This appendix is derived from the gawk-3.0.0 and regex-0.12
manuals.
A regular expression, or regexp, is a way of describing a set of strings. The simplest regular expression is a sequence of letters, numbers, or both. Such a regexp matches any string that contains that sequence. Thus, the regexp `foo' matches any string containing `foo'. Other kinds of regular expressions let you specify more complicated classes of strings.
Gcal uses exactly one of the following regular expression programming libraries respectively methods, and that in the decreasing priority how it is chosen at configuration time, or better, compile time of the software:
@multitable @columnfractions .05 .75 .2
re_compile_pattern() and `regex.h'
@tab GNU-REGEX
regcomp() and `regex.h'
@tab POSIX-REGEX
re_comp()
@tab BSD-REGEX
regcmp()
@tab SysV-REGEX
regcomp() and `regexp.h'
@tab V8-REGEX
NO-REGEX
Try `gcal --version' for detecting the kind of regular expression
programming library respectively method that is burned-in in your Gcal program!
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