#! /usr/bin/env perl
use strict;
use warnings;
use Getopt::Long;

$| = 1;             # unbuffered STDOUT


# save command and cmdline arguments for later re-use
# because GetOptions modifies @ARGV
my @cmdline = ( $0, @ARGV );


GetOptions(
    \my %OPT,
    'timeout=i',
) or exit 255;

die "(E) No timeout specified.\n"   unless $OPT{timeout};

my @command = @ARGV;


my $pid = open my $pipe, '-|', @command
    or die "(E) Could not open pipe to command '@command': $!";

print "pid $pid : @command\n";

while ( 1 ) {
    my $line;

    # read from $pipe; must be successful within $OPT{timeout} seconds
    eval {
        local $SIG{ALRM} = sub { die "alarm\n"; };
        alarm $OPT{timeout};
        $line = <$pipe>;
        alarm 0;
    };

    # timeout exceeded
    if  ( $@ ) {
        die "(E) error in alarm...\n"   if $@ ne "alarm\n";
        print "ALARM received!\n";
        exec( @cmdline ) or die "(E) Could not re-execute myself: $!";
    }
    # just in time
    else {
        print "READ: $line";
    }
}

__END__