james28909 has asked for the wisdom of the Perl Monks concerning the following question:

Hello monks, I am back, and come with a question regarding opening a file with undef as the filename.

open (my $fh, '+>', undef);

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What exactly is this doing? I ask this because I was able to read and write to $fh as if it were a real file. Is it a temp file somewhere on the harddrive? Or is it in memory

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Re: Open with 'undef' filename.
by BrowserUk (Patriarch) on Nov 07, 2016 at 00:14 UTC
    From perlfunc:open
    As a special case the 3-arg form with a read/write mode and the third argument being undef: open(my $tmp, "+>", undef) or die ... opens a filehandle to an anonymous temporary file.

    I believe the term "anonymous temporary file" is related to this on *nix. I know nothing more about that.

    On Windows it creates a very ordinary file in the users home directory with a name of plx????.tmp where ???? are 4 hex digits. And those files are automatically delete when the process ends.

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      Thanks for the explanation.

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