FAQ 5.6 How do I make a temporary file name?

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

This is an excerpt from the latest version perlfaq5.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .


5.6: How do I make a temporary file name?

    If you don't need to know the name of the file, you can use "open()"
    with "undef" in place of the file name. The "open()" function creates an
    anonymous temporary file.

            open my $tmp, '+>', undef or die $!;

    Otherwise, you can use the File::Temp module.

            use File::Temp qw/ tempfile tempdir /;

            $dir = tempdir( CLEANUP => 1 );
            ($fh, $filename) = tempfile( DIR => $dir );

            # or if you don't need to know the filename

            $fh = tempfile( DIR => $dir );

    The File::Temp has been a standard module since Perl 5.6.1. If you don't
    have a modern enough Perl installed, use the "new_tmpfile" class method
    from the IO::File module to get a filehandle opened for reading and
    writing. Use it if you don't need to know the file's name:

            use IO::File;
            $fh = IO::File->new_tmpfile()
            or die "Unable to make new temporary file: $!";

    If you're committed to creating a temporary file by hand, use the
    process ID and/or the current time-value. If you need to have many
    temporary files in one process, use a counter:

            BEGIN {
            use Fcntl;
            my $temp_dir = -d '/tmp' ? '/tmp' : $ENV || $ENV;
            my $base_name = sprintf "%s/%d-%d-0000", $temp_dir, $$, time;

            sub temp_file {
                    local *FH;
                    my $count = 0;
                    until( defined(fileno(FH)) || $count++ > 100 ) {
                            $base_name =~ s/-(\d+)$/"-" . (1 + $1)/e;
                            # O_EXCL is required for security reasons.
                            sysopen FH, $base_name, O_WRONLY|O_EXCL|O_CREAT;

                    if( defined fileno(FH) ) {
                            return (*FH, $base_name);
                    else {
                            return ();


The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in

Site Timeline