regex - What are the differences between glob-style pattern and regular expression?

Question

I've encountered situations where only glob-style patterns are supported and full regular expression support is not there, for instance redis keys. I'd like to know the distinction between the two. Also it makes me wonder, is implementing regex matching algorithm way harder compared to glob-style pattern that some softwares doesn't support regex at all?

Answer 1

Traditional glob wildcards support a very narrow set of metacharacters — * is "anything", ? is an arbitrary single character; Bourne shell also supports [a-z123] for a single character out of a set of alternatives, and [!x-z789] any one except those listed.

Regex obviously is much richer, supporting repetitions, and (in ERE) alternation and specific numbers of repetitions. Perl-style regex further extends the formalism to the point where multiple books have been written, and more will be.

Basic regex is not altogether a lot more challenging to program than glob wildcards, and these days, a competent programmer would link to an existing library in either case, anyway.

Many simpler systems don't want to burden their users with the complexity of learning regular expressions — even basic wildcards are a challenge to explain to your average sales guy^W^W person who isn't a full-time computer user.