Hi,

I want to find out if "do there exist any *.test files in a certain directory" on a certain set of directories.

Given:     sub myglob { my @g = glob shift; @g }

What is the difference between these two statements: 

    if (glob "$dir/*") { print "glob $dir: yes\n"; }

    if (myglob "$dir/*") { print "myglob $dir: yes\n"; }

[download]
?

They both work the "first time" they are invoked, but if I have a loop to check more than one directory, 'glob' works at first EVERY OTHER call; here is a whole program: 

#!/usr/bin/perl -w
    
sub glob2 { glob(shift); }
sub myglob { my @g = glob(shift); @g }
    
use strict; use diagnostics;
    
my @dirs = ('dir1', 'dir2', 'dir3', 'dir4', 'dir5', 'dir6');
#my @dir_x = '~';
my @dir_x = '/bin';
#my @dir_x = '/dir-fake-root';
my @fakedirs = ('dir-fake1', 'dir-fake2');

map { mkdir($_,0777) ; local *F; open(F,">$_/x.test") && close(F) || d
+ie; } @dirs;

for my $dir (@dirs, @fakedirs, @dir_x, @dirs, @fakedirs) {

        print "$dir/*: ";
        
        if (myglob("$dir/*")) { print "myglob "; }
        if (glob  ("$dir/*")) { print "glob ";   }
        if (glob2 ("$dir/*")) { print "glob2 ";  }
        print "\n";

}

map { unlink("$_/x.test") || die; rmdir($_) || die; } @dirs;

[download]

On both v5.6.1 cygwin and v5.005_03 linux, perl produces these results: 

dir1/*: myglob glob glob2
dir2/*: myglob
dir3/*: myglob glob glob2
dir4/*: myglob
dir5/*: myglob glob glob2
dir6/*: myglob
dir-fake1/*:
dir-fake2/*:
/bin/*: myglob glob glob2
dir1/*: myglob glob glob2
dir2/*: myglob glob glob2
dir3/*: myglob glob glob2
dir4/*: myglob glob glob2
dir5/*: myglob glob glob2
dir6/*: myglob glob glob2
dir-fake1/*: glob glob2
dir-fake2/*: glob glob2

[download]

As you can see, glob2 behaves like glob in all respects. myglob always works correctly. Before globbing /usr/*, glob correctly globs an existing directory every other call, and correctly doesn't find nonexistant directories.

After globbing /usr/*, glob then reports 'true' to every directory, even nonexistant ones (however, globbing /nonexistant-dir/* instead of /usr/* would kept glob working as it did the first time).

So what is the difference between the myglob defined here and regular glob? This is probably a caveat in perl scoping or contexts that I don't know about - I just learned perl last week to write a testsuite. And is there a better way to check for existance of any files in a given directory (opendir/readdir maybe)?

--thanks

Edit: chipmunk 2001-07-18

In reply to glob weirdness / list contexts? by giantfish

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