This sub ensures that a unique filename is available for purposes such as generating a backup file before performing some sort of file maipulation, or for when a unique temporary file is required 
sub get_unique_filename {
    my ( $name, $max_tries ) = @_;
  return if not -e $name;
    $name =~ s/(\.[^\.]+)$//;
    my $ext = $1 ? $1 : '';
    my $tries = 1;
    my $max_tries ||= 100;
    while (  -e $name.$tries.$ext ) {
        $tries++;
        die "Could not make a unique filename for $name$ext\n" if $tri
+es > $max_tries;
    }
  return $name.$tries.$ext;
}

[download]

Replies are listed 'Best First'.
Re (tilly) 1: Unique filename
by tilly (Archbishop) on May 22, 2001 at 21:33 UTC
    I recommend File::Temp for a better version of this wheel.
[reply]
(tye)Re: Unique filename
by tye (Sage) on May 22, 2001 at 20:50 UTC

    This generates a classic race condition. To avoid that you need to have this function open the file with the O_EXCL flag specified and then retry with the next free file name if that fails.

            - tye (but my friends call me "Tye")
[reply]

      Hmm, I have to concur. Just wrapped the code around the regex without sufficient thought. Given that its function it should really pass back a locked filehandle for writing. On the to do list 

      $\=' ';
sub AUTOLOAD{@_=caller();print shift}
package Back;&::;
package To;&::;
package The;&::;
package Drawing;&::;
package Board;&::;

      [download]
      tachyon
[reply]
[d/l]
Re: Unique filename
by shelob101 (Sexton) on May 27, 2001 at 00:41 UTC
    here's what I use, there may be "race condition" issues with it but I've had it in production for a couple of years with no problems: 
    $filename="/data/base_file.";
$x=0;
$x++ while (-e $filename.$x);
$realfile=$filename.$x;

    [download]
[reply]
[d/l]
Re: Unique filename
by John M. Dlugosz (Monsignor) on Jun 07, 2001 at 23:54 UTC
    A simple way to make a unique filename is to to use a GUID (aka UUID). No races, no checking needed!
[reply]

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