#!/usr/bin/perl -w
use strict;
my $pid=$ARGV[0];
my $trace_out;
my $strace_pid;

eval {
  local $SIG{ALRM} = sub {
    kill 2, $strace_pid || warn "couldn't kill $strace_pid: $!";
    close STRACE or die "couldn't close strace";
    die "exiting eval";
  };
  $strace_pid = open (STRACE,"strace -q -p$pid 2>&1|") or die "couldn't open strace";
  alarm (1);
  undef $/;
  $trace_out=<STRACE> ;
};

print "traceout is $trace_out";

##</code><code>##

#!/usr/bin/perl
use Fcntl ':flock';
open FH, "file.txt" ;
flock FH, LOCK_EX or die "couldn't lock";
while (true) {};

##</code><code>##

>./locker.pl &
[1] 17289
>./locker.pl &
[2] 17290
>strace -q -p17289
>strace -q -p17290
flock(3, LOCK_EX <unfinished ...>

##</code><code>##

./hang_finder 17290
traceout is 

##</code><code>##

traceout is flock(3, LOCK_EX