For generating, say, unique temporary files, use
IO::File::new_tmpfile. In addition there's the
POSIX::tmpnam() function which would get you a unique filename (subject to a race condition, however, since there's a period between when it's generated and when it's used).
In a pinch, use something like this:
$num = 12345;
$dir = "/some/dir/";
$num++ while -e "$dir/$num";
open(F, ">$dir/$num") or die ...
But of course, there's still a race condition. A more secure solution would be to take advantage of
sysopen and O_EXCL to iterate through filenames:
use Fcntl;
use FileHandle;
$num++ while !sysopen(F, "$dir/$num", O_EXCL|O_CREAT, 0777) && $! eq "
+File exists";
die "$dir/$num: $!" if $!;
Once you start adding all of the bells and whistles, though, you're just re-implementing
IO::File new_tmpfile.
