Re: Using Linux Commands in Perl

See the pipe-form of open:

my $cmd = 'netcat localhost 12345 |';
my $pid = open my $netcat, $cmd
    or die "Couldn't spawn [$cmd]: $!";

for (1..100) {
    my $line = <$netcat>;
    print $line;
};

END {
    # Clean up leftover processes
    kill 9 => $pid
        if $pid;
};
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Comment on Re: Using Linux Commands in Perl - `Backticks` Download Code

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Re^2: Using Linux Commands in Perl - `Backticks` by JavaFan (Canon) on Sep 30, 2010 at 21:47 UTC
The OP asked to have it run for 100ms, not 100 lines. Your program may hang for an unknown time, it may be days before you've read 100 lines. I would open a pipe, use a select loop and sysread to read from the pipe. After 100ms, terminate the loop and the pipe.	[reply]
Re^3: Using Linux Commands in Perl - `Backticks` by Corion (Patriarch) on Sep 30, 2010 at 22:16 UTC
Duh - I misread that. In that case, using select and alarm is likely the best approach. Luckily, the question is about Linux, where this approach will work. On Windows, reading from a pipe does not play well with select and/or IO::Select. The approaches of tunnelling the IO through (TCP) sockets (in the Win32 mkpipe emulation) do work for certain cases and horribly fail for other cases, always depending on the program spawned in such a fashion.	[reply]
Re^4: Using Linux Commands in Perl - `Backticks` by JavaFan (Canon) on Oct 01, 2010 at 08:54 UTC
Considering that select() already has a timeout, why would you use alarm?	[reply]
Re^5: Using Linux Commands in Perl - `Backticks` by Corion (Patriarch) on Oct 01, 2010 at 12:31 UTC
Re^6: Using Linux Commands in Perl - `Backticks` by JavaFan (Canon) on Oct 01, 2010 at 13:43 UTC
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Re^2: Using Linux Commands in Perl - `Backticks` by ThirtySecondNoob (Novice) on Sep 30, 2010 at 23:20 UTC
Thank you so much... This works perfectly! I originally wanted to get one line, parse it, and move on to the next line, so I had thought that there was a netcat -option that would have it timed for you. This works much better, and I can get to the good stuff for the code now. Hopefully I can get some practice piping now, too. :)	[reply]