in reply to Re^2: fork - alarm - output
in thread fork - alarm - output

Isn't this just easier? 

#! perl -slw
use strict;

my $pid = open IN, '-|',
    qq[ perl -E"say scalar localtime, sleep 1 for 1.. $ARGV[0]" ]
    or die $!;

eval {
    local $SIG{ ALRM } = sub {
        kill -9, $pid;
        warn 'timeout';
    };
    alarm 5;
    waitpid $pid, 0;
    alarm 0;
};

while( <IN> ){
   print;
}

__END__
c:\test>junk 3
Tue Jun  8 15:33:04 20101
Tue Jun  8 15:33:05 20101
Tue Jun  8 15:33:06 20101

c:\test>junk 4
Tue Jun  8 15:33:09 20101
Tue Jun  8 15:33:10 20101
Tue Jun  8 15:33:11 20101
Tue Jun  8 15:33:12 20101

c:\test>junk 5
timeout at C:\test\junk.pl line 11.

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    Re^4: fork - alarm - output
    by ikegami (Patriarch) on Jun 08, 2010 at 15:45 UTC
      Only if the child prints less than a pipe's buffer's worth of information (64k?). That's very small these days.
    		[reply]
        Only if the child prints less than a pipe's buffer's worth

        That (conservatively), probably covers 85% of the uses of such code. Are you telling me that you don't see a relatively simple modification to cater for the rest?

        I mean without resorting to forks & execs and no-blocks and selects and events&globals, state-driven spaghetti code?

        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
    		[reply]

          That (conservatively), probably covers 85% of the uses of such code.

          I don't buy that statistic. Either way, it sounds like you're saying 1 failure in 5 attempts is ok!

          Are you telling me that you don't see a relatively simple modification to cater for the rest?

          Are you saying we're suppose to assume everyone knows that modification is needed and that it was there all along, whatever it might be?

          Anyway, I don't call the following a simple modification. 

          my $pid = open IN, '-|',
    qq[ perl -E"say scalar localtime, sleep 1 for 1.. $ARGV[0]" ]
    or die $!;

my $buf = '';
if (!do {
    local $SIG{ ALRM } = sub {
        kill -9, $pid;
    };
    alarm 5;
    $buf .= $_ while <IN>;
    waitpid($pid, 0);
    alarm 0;
    die("Can't waitpid: $!\n")                      if $? == -1;
    die("Child killed by signal ".($? & 0x7F)."\n") if $? & 0x7F;
    die("Child returned error ".($? >> 8)."\n")     if $? >> 8;
    1
}) {
    waitpid($pid, 0);
    die("Timeout\n");
}

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