versioning - A regex for version number parsing

Question

I have a version number of the following form:

version.release.modification

where version, release and modification are either a set of digits or the '*' wildcard character. Additionally, any of these numbers (and any preceding .) may be missing.

So the following are valid and parse as:

1.23.456 = version 1, release 23, modification 456
1.23     = version 1, release 23, any modification
1.23.*   = version 1, release 23, any modification
1.*      = version 1, any release, any modification
1        = version 1, any release, any modification
*        = any version, any release, any modification

But these are not valid:

*.12
*123.1
12*
12.*.34

Can anyone provide me a not-too-complex regex to validate and retrieve the release, version and modification numbers?

Answer 1

I'd express the format as:

"1-3 dot-separated components, each numeric except that the last one may be *"

As a regexp, that's:

^(d+.)?(d+.)?(*|d+)$

[Edit to add: this solution is a concise way to validate, but it has been pointed out that extracting the values requires extra work. It's a matter of taste whether to deal with this by complicating the regexp, or by processing the matched groups.

In my solution, the groups capture the "." characters. This can be dealt with using non-capturing groups as in ajborley's answer.

Also, the rightmost group will capture the last component, even if there are fewer than three components, and so for example a two-component input results in the first and last groups capturing and the middle one undefined. I think this can be dealt with by non-greedy groups where supported.

Perl code to deal with both issues after the regexp could be something like this:

@version = ();
@groups = ($1, $2, $3);
foreach (@groups) {
    next if !defined;
    s/.//;
    push @version, $_;
}
($major, $minor, $mod) = (@version, "*", "*");

Which isn't really any shorter than splitting on "." ]