opendir or not?

elbow has asked for the wisdom of the Perl Monks concerning the following question:

In my quest to amend an email conversion script, I've come across the following code to pull out files from a directory:-

while ($file = <$dir\\*.txt>) {
  #do your stuff
}
[download]

Whenever I have had to access files from a directory before I've used the approach:-

opendir    ( DIR, $dir )      || die "Cannot open directory $dir: $!";
while ( defined( $file = readdir(DIR) ) ) {
  next if $file =~ /^\.\.?$/;      
  if ( $file =~/txt$/ ) {
    #do your stuff
  }
}
closedir DIR;
[download]

Benchmarking shows only a small difference in performance, with opendir the slightly better of the two.

All I want to know is - is there any other difference between the two approaches that I should take into account?

Or am I fussing over nothing? :-}

elbow

Update - I take back the slight difference part - benchmarking shows a huge difference between the two pieces of code on a directory with a lot of *.txt files in!

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Re: opendir or not? by davido (Cardinal) on Feb 02, 2004 at 09:06 UTC
There's nothing inherently wrong with the glob approach you're using with the <> operator. The POD does warn against variable interpolation within a <> operator for readability reasons (perlop section on the < > operator): If you're trying to do variable interpolation, it's definitely better to use the glob() function, because the older notation can cause people to become confused with the indirect filehandle notation. `@files = glob("$dir/*.[ch]"); @files = glob($files[$i]);` [download] Seems like a pretty minor nit. It sounds like you're fine. Dave	[reply] [d/l]
Re: opendir or not? by Hena (Friar) on Feb 02, 2004 at 09:49 UTC
Unless i read that wrong, then its not quite as portable. Eg. might not work for win or platform X that doensn't use "/" as path separator. Also consider filename 'my_file/with funky sep'.	[reply]
Re: opendir or not? by halley (Prior) on Feb 02, 2004 at 15:21 UTC
You mentioned twice that there's a benchmark discrepancy between the while loop and the readdir loop. While you're in a benchmarking mood, if you're so inclined, please show us the results of the three forms: `while ($eachfile = <.txt>) { ... }` [download] `@files = <.txt>; foreach (@files) { ... }` [download] `opendir(DIR, ...); while (defined ($eachfile = readdir(DIR) )) { next if not /\.txt$/; ... }` [download] Of course, there's platform differences to consider, too. Some filesystems bog down worse than others with long directories. If you're bored, check that `@files = <.txt>` is really just as fast as `@files = glob(".txt")`, too. -- `[ e d @ h a l l e y . c c ]`	[reply] [d/l] [select]