The module File::MkTemp seems to be what you want:

use File::MkTemp;

$dir = '.'; # directory to create file in
$string = mktemp('tempXXXXXX',$dir);
open(F,$string);
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Will return a unique file name, you can also have it return a unique file handle so that there is no chance of opening an identical file in two instances of your script:

use File::MkTemp;

$dir = '.'; # directory to create file in
$fh = mkstemp('tempXXXXXX',$dir);
print $fh "stuff";
$fh->close;
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You can add more 'X's, but you need at least six.

In a pinch, use something like this:

$num = 12345;
$dir = "/some/dir/";

$num++ while -e "$dir/$num";

open(F, ">$dir/$num") or die ...
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use Fcntl;
use FileHandle;

$num++ while !sysopen(F, "$dir/$num", O_EXCL|O_CREAT, 0777) && $! eq "
+File exists";

die "$dir/$num: $!" if $!;
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$filename = $$.time;
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Actually, that wouldn't prevent duplicate filenames at all, depending on how fast you're generating filenames. For example, look what the following does:


while (1) {
    print $$.time."\n";
}
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Also, on Win32, there's a non-zero chance of a PID being reused.

When you log into a site, you have two options.
You can start running a script from a new connection or you can use an existing connection.
Since only one person can be using a PID at a time, the combination of time and PID is fine.

my $outfile = localtime;
print "$outfile\n";
$outfile=~s/\s|://g;
$outfile="$outfile" . rand($outfile);
$outfile=~s/\.//g; #for win32 - doesn't like multiple dots
print $outfile;
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do {
$newfilename = $$.time();
} until (!-e $newfilename);
print $newfilename;

# and then do your stuff
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-- tune

Since $$ doesn't change, you've effectively created a busy-wait sleep. Why not just stick a sleep 1 in there instead?

-- Randal L. Schwartz, Perl hacker

but the existing file can be removed by another thread in less time than 1 second. I understand why I have got downvoted, but the point is not on the method of creating the unique filename it is on how to avoid overwrinting the existing file.

-- tune