Hacker News Reader

Comment by tombert | Hacker News Reader

You know I googled this immediately after I posted it, and you're absolutely right, but a good chunk of the syntax still kind of looks like regular expressions so I don't think I was too far off!

View on HN

Regular expressions and glob(7) expressions look superficially similar, but it is mostly an illusion; they both use * and ? as common metacharacters, but both of those characters mean different things in the two systems. Only the [ and ] characters are used more similarly, but even those have their differences. The two syntaxes only have one common function which functions identically in the two systems, but it is invoked by different characters; specifically the ? (question mark) character in glob(7) exactly corresponds to the . (full stop) character in regular expressions.

To be pedantic: You're conflating the syntax of regular exprssions, with the (computer science) concept. Glob patterns are a kind of very resticted regular pexressions. Ksh extended the glob syntax so it has the full power of regular expressions in the computer science sense - though without all the extensions of modern regular expressions.

No, globs are not regular expressions.

“Globs do not include syntax for the Kleene star which allows multiple repetitions of the preceding part of the expression; thus they are not considered regular expressions, which can describe the full set of regular languages over any given finite alphabet.”

— <https://en.wikipedia.org/w/index.php?title=Glob_(programming...>

You're right, normal globs are not regular expressions regardless of syntax. Parent is correct too, ksh globs are regular expressions. See shopt -s extglob in bash, setopt kshglob in zsh (extendedglob for zsh's native, IMO inferior, quantifier syntax).

Reply on news.ycombinator.com