Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl Monk, Perl Meditation
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
I'm trying to figure out an effective way of timing out shell commands in Perl. At several places I've looked the canonical solution appears to be something like...
eval { local $SIG{ALRM} = sub { die "TIMEDOUT" }; alarm(10); <command> alarm(0); }; if ($@) { die $@ unless $@ =~ /TIMEDOUT/; # command timed out ... } ...
If "command" is an internal perl command this works fine. If it is an external comand (e.g. system(), backticks, etc.) the code above is executed just fine, but the child continues to execute as well rather than dying on the spot.

I guess I should expect this since I'm assuming that the exception has longjmp'd past the code that would reap the child. I suppose another way of handling this would be to use a pipe open like this...

$pid = open(PIPE, "$command |") or die $!; eval { local $SIG{ALRM} = sub { die "TIMEDOUT" }; alarm(10); while (<PIPE>) { <do whatever> }; close(PIPE); alarm(0); }; if ($@) { die $@ unless $@ =~ /TIMEDOUT/; kill 9, $pid; close(PIPE); ## needed?? $? ||= 9; }
I'm probably being overly paranoind, but this all seems rather cheesy. If the close is outside the eval, it seems like it won't catch cases where the child closes STDOUT/STDERR but decides not to quit (not sure if that happens much). If it is inside the eval, as above, will things get cleaned up properly within Perl if the code breaks out while in the close? Is there something better?

Thanks


In reply to Timing out shell commands (paranoia) by bluto

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others cooling their heels in the Monastery: (9)
    As of 2014-12-23 03:08 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      Is guessing a good strategy for surviving in the IT business?





      Results (134 votes), past polls