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

Hey,

The documentation states: "The make_path function creates the given directories if they don't exists before.

Still, 

make_path $path or die "Couldn't create tmp dir: $!\n";

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keeps on giving me plenty of "Couldn't create tmp dir: File exists".

I even tried surrounding the whole thing with if (!-e $path) { ... }, but of course that doesn't help in case of a race condition, since several instances of the script are forked off in my code. But shouldn't make_path deal with this by default?

I need to sit down and work through the "Error handling" part because I don't understand it yet, but will that help at all in my case, with several instances of the script all trying to create the directory before writing to it?

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Re: Problem with make_path in File::Path
by MidLifeXis (Monsignor) on Jul 20, 2012 at 16:24 UTC

    Let's assume the simplest case - you run the make_path call with the same parameters twice in a row. Assume that the first time the $path does not exist. The second time, since the $path already exists, the function returns a value of (), which is false, triggering the die.

    See the documentation for File::Path for more details.

    Update: Change the return value from 0 to ()

    --MidLifeXis

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      ***argh***

      I'll admit it is implicit in "...in scalar context (the function returns) the number of directories created", but there is no way I would have got it without your help! Reading between the lines that way presupposes much more experience with Perl.

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Re: Problem with make_path in File::Path
by toolic (Bishop) on Jul 20, 2012 at 17:14 UTC
    Keep reading the doc for File::Path:
    The function returns the list of directories actually created during the call; in scalar context the number of directories created.
    If make_path makes a directory which didn't already exist, it returns 1, which means the die is not executed.

    If make_path does not need to make a directory because it already exists, it returns undef, which means the die is executed. But, you do not want it to die because you are emulating 'mkdir -p'.

    Just use: 

    make_path $path;

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    Or, use error => \$err as specified in the docs.

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