Question

I have a config .ini file where users can specify a file pattern either using a Perl regular expression or as an Ant globbing pattern. The following for instance would prohibit a user from creating a file that’s not allowed under Windows:

[BAN Defined using Ant Globbing]
file = **/prn.*
ignorecase = true

[BAN Defined using Regular expressions]
match = /(aux|con|com[0-9]*|lpt[0-9]*|nul|clock$)\.?[a-z]$
ignorecase = true

Right now, I have to convert the glob into a regular expression in order to programmatically handle it. I have a routine that does it, but it’s kind of convoluted. I am looking for one of the following:

• An easy way of converting a glob into a regular expression
• Methods of matching glob expressions like you can with regular expressions.

For example:

 if ($regex =~ /\/(aux|con|com[0-9]*|lpt[0-9]*|nul|clock$)\.?[a-z]$) {
 if ($glob ?magic? /**/prn.*/) {

I was hoping that there is some magical Perl way of doing this. So, is there an easy can’t miss way of doing this:

BTW, here’s my subroutine in case anyone is interested:

sub glob2regex {
    my $glob = shift;

    my $regex = undef;
    my $previousAstrisk = undef;

    foreach my $letter (split(//, $glob)) {
        #
        #    ####Check if previous letter was astrisk
        #
        if ($previousAstrisk) {
            if ($letter eq "*") { #Double astrisk
                $regex .= ".*";
                $previousAstrisk = undef;
                next;
            } else {        #Single astrisk: Write prev match
                $regex .= "[^/]*";
                $previousAstrisk = undef;
            }
        }
        #
        #   ####Quote all Regex characters w/ no meaning in glob
        #
        if ($letter =~ /[\{\}\.\+\(\)\[\]]/) {
            $regex .= "\\$letter";
            #
            #   ####Translate "?" to Regular expression equivelent
            #
        } elsif ($letter eq "?") {
            $regex .= ".";
            #
            #   ####Don't know how to handle astrisks until  the next line
            #
        } elsif ($letter eq "*") {
            $previousAstrisk = 1;
            #
            #   ####Convert backslashes to forward slashes
            #
        } elsif ($letter eq '\\') {
            $regex .= "/";
            #
            #   ####Just a letter
            #
        } else {
            $regex .= $letter;
        }
    }
    #
    #   ####Handle if last letter was astrisk
    #
    if ($previousAstrisk) {
        $regex .= "[^/]*";
    }
    #
    #    ####Globs are anchored to both beginning and ending
    #
    $regex = "^$regex\$";
    return $regex;
}

Answer 1

Apparently, there’s no neat Perl Guru trick for creating a regular expression from a glob. Drats.

The best I can do is find a CPAN module like Text::Glob that does it. However, Text::Glob doesn’t do Ant style expanded globbing, so I’d have to modify it anyway. And, the code is no simpler than what I already have.

So, I’m just sticking with what I have.

Thanks anyway.