Question

I’m building a regression system (not unit testing) for some Perl scripts.

A core component of the system is

  `perl script.pl @params 1>stdoutfile 2>stderrfile`;

However, in the course of actually working on the scripts, they sometimes don’t compile(Shock!). But perl itself will execute correctly. However, I don’t know how to detect on stderr whether Perl failed to compile (and therefore wrote to stderr), or my script barfed on input (and therefore wrote to stderr).

How do I detect whether a program executed or not, without exhaustively finding Perl error messages and grepping the stderr file?

Answer 1

It might be easiest to do this in two steps:

system('$^X -c script.pl');
if ($? == 0) {
    # it compiled, now let's see if it runs
    system('$^X script.pl', @params, '1>stdoutfile', '2>stderrfile');
    # check $?
}
else {
    warn "script.pl didn't compile";
}

Note the use of $^X instead of perl. This is more flexible and robust. It ensures that you’re running from the same installation instead of whatever interpreter shows up first in your path. The system call will inherit your environment (including PERL5LIB), so spawning a different version of perl could result in hard-to-diagnose compatibility errors.