in reply to Re: Re: Passing function to a function using \&<function name> method
in thread Passing function to a function using \&<function name> method

Does anyone know why the timeout does not work when I use the `<system command>` for performing system commands?

No. I tested it with `cmd`, and it works fine for me. I am on Linux, and it sounds like you are on Win32, so maybe it's an OS thing with signals? *shrug*.

In the timeout_func function, is there a way of getting the function name from the coderef somehow ... ?

Not that I know of. You could get the name of the function from within the function itself with (caller 0)[3], but that won't help you in timeout_func (unless you set a package variable or something yucky like that). You could resort to using symbolic refs, though it's playing with fire...

timeout_func($timeout, 'myfunc', ...);

sub timeout_func
{
    my ($timeout, $func_name, @args) = @_;
    
    # ...

    eval
    {
        # ...
        {
            no strict 'refs';
            $func_name->(@args);
        }
    }
    
    if ($@)
    {
        die "$func_name died ($@)\n";
    }
}

[download]

Notice that you pass the name of the function to call, instead of a hard reference to the function (the \&myfunc syntax).

--
edan (formerly known as 3dan)

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Re: Re: Re: Re: Passing function to a function using \&<function name> method
by Anonymous Monk on Feb 14, 2004 at 17:00 UTC
    Hi edan,

    Thanks for your posting.

    I have tried both types of system command method and Linux and found the timeout to work. So it is a Windows32 problem.

    Do you know how I can find out more about the timeout not working when I use the `<system command>` method?

    I have read your suggestion about finding out the name of a function that has been passed into a function and am not sure on doing anything that is playing with fire.

    Do you know what makes this method playing with fire?

    Thank you. Richard Thomas.
[reply]

      Do you know how I can find out more about the timeout not working when I use the `<system command>` method?

      You might want to look at your local (ActiveState?) perl documentation about the alarm function. Perhaps it's not implemented, or partially implemented? Or Google. Don't know what else to tell you.

      Do you know what makes this method playing with fire?

      Using symbolic references is generally considered a bit risky, unless you really know what you are doing, because (among other reasons) you can cause some very hard to find bugs when you start using them. Do a Super Search for 'symbolic references' (or 'refs', etc.) to find out what other Monks have to say about them. Here is a recent thread about them, to get you started: variables names used to define variables. Basically, they can be a handy feature, but only if you're careful, and there is frequently a better way to do things.

      --
      edan (formerly known as 3dan)

[reply]
        Hi edan,

        Thanks for this information, it is very useful.

        What I have realised is that I would like to take my system call functionality further.

        At the moment, the way I have coded it is that the PERL script can gain control back when it has launched an external program/command or script with the system(<command>) or `<command>` method in the event of a timeout.

        What I would like to do now is if the timeout is reached, I kill off the process that was launched.

        I realised that I would need the PID and am not sure if it would be available from these methods. If the PID is not available from the above methods, what other method can I use to kill off an external program/command or script that PERL has launched once a timeout has reached? Would it be something like a spawn method or something like that?

        If there is a Unix only solution to this, then I would still be interested. I mainly to initial testing on Windows, then move onto Red Hat Linux for proper testing and implementation.

        Thanks,

        Richard Thomas.
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