Find a file in a list of directories

Description:

This snippet searches a series of directories for a file. For instance, you may want to open the file 'foo.txt', but it could be in any one of a number of directories, so you want to search them one after the other until you find it.

An analogy would be the way a shell finds a program based on the value of the PATH environment variable.

asdfgroup's remarks noted.

    my $target = 'foo.txt';
    my $file = do {
        my $target = undef;
        foreach my $dir( qw{ /tmp /var/tmp /foo /bar } ) {
            my $t = "$dir/$target";
            # nb: you might want to use -e here
            # but -f might be what you *really* want, YMMV
            if( -f $t ) {
                $target = $t;
                last;
            }
        }
        $target;
    };

    if( $target ) {
        open IN, $target or die "Cannot open $target for input: $\n";
        # ...
    }
    else {
        die "Can't find $target.\n";
    }

Comment on Find a file in a list of directories Download Code

Replies are listed 'Best First'.
Re: Find a file in a list of directories by asdfgroup (Beadle) on Apr 25, 2002 at 15:27 UTC
more compact version of your code. And you should use '-e' test instead of '-t' `#!/usr/bin/perl sub FileFinder { my ($target, @dir) = @_; return (grep {-e $_} map {"$_/$target"} @dir)[0]; } open(F, FileFinder('FileFinder.pl', qw(some/ dirs/ ./)) \|\| die "File n +ot found") or die $!;` [download]	[reply] [d/l]
Re: Re: Find a file in a list of directories by demerphq (Chancellor) on May 06, 2002 at 16:50 UTC
IMO in general grep and map shouldn't be chained together, map can do greps job without having retraverse the array. `return (map{-e "$_/$target" ? "$_/$target" : ()} @dir)[0];` [download] And frankly why bother with map and grep at all? This is much more efficient. `sub FileFinder { my $target=shift; -e "$_/$target" && return "$_/$target" foreach @_; undef }` [download] Oh and before the premature optimization police arrest me, remember that we are searching a filesystem (possible remote etc) here. That call to -e could take a while and if we have to do more of them than we really need to then we could end up wasting a lot of time. Adjust the file test to your taste ;-) Yves / DeMerphq --- Writing a good benchmark isnt as easy as it might look.	[reply] [d/l] [select]


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