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

Can anyone point me to a quick table of what functions errors into which of the two variables, $! or $?. I always get confused and it makes me spiritually angry.

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Re: $! or $?
by kschwab (Vicar) on Jan 31, 2001 at 01:28 UTC
    See perlvar, it's pretty clear. 

    $!  aka $ERRNO      
            If used in a numeric context, yields 
            the current value of errno, with all
            the usual caveats.  
$?  aka $CHILD_ERROR
             The status returned by the last pipe 
             close,  backtick(``) command, or 
             system() operator. 
$@  aka $EVAL_ERROR
             The Perl syntax error message from the 
             last eval() command

    [download]
    So unless the error is in the context of starting a new process, or an eval(), it's $! you want.

    One possible exception: Modules may use some variable or method of their own to expose errors. See the docs for the module.

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[d/l]
Re: $! or $?
by c-era (Curate) on Jan 31, 2001 at 01:24 UTC
    $! - os error - from the last system call (not to be confused with 'system()')

    $? - child error - The status returned by the last pipe close ('`', 'system()')

    '`' and 'system()' create child processes that run and terminate. $? contains their exit status. Other calls ('open()', 'close ()',etc.), make system calls, and $! contains the status of the last system call.

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Re: $! or $?
by dkubb (Deacon) on Jan 31, 2001 at 12:21 UTC
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