IO::Pipe hangs

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: IO::Pipe hangs by BrowserUk (Patriarch) on Sep 20, 2012 at 19:14 UTC
Because you haven't emptied the pipe, which means that tasklist is blocked waiting to finish writing to it. Just closing the pipe won't allow tasklist to end; the pipe won't close until it does. Deadlock. The answer is to empty the pipe before closing it: `use strict; use warnings; use IO::Pipe; my $cmd = "tasklist"; my $pipe = IO::Pipe->new(); $pipe->reader($cmd); while (my $line = $pipe->getline()) { print $line; last if $line =~ /^smss/; } 1 while $pipe->getline; $pipe->close();` [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' 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. RIP Neil Armstrong	[reply] [d/l]
Re^2: IO::Pipe hangs by Anonymous Monk on Sep 20, 2012 at 19:16 UTC
OK, thanks.	[reply]
Re: IO::Pipe hangs by choroba (Cardinal) on Sep 20, 2012 at 19:17 UTC
On Linux, it works (I used "ps x" as the command and `/alpine/` as the regex.) لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l]
Re^2: IO::Pipe hangs by Anonymous Monk on Sep 20, 2012 at 19:28 UTC
On Solaris it works as well. Something wrong with Windows implementation? C:\>perl -v This is perl 5, version 14, subversion 2 (v5.14.2) built for MSWin32-x +64-multi-thread (with 1 registered patch, see perl -V for more detail) Copyright 1987-2011, Larry Wall Binary build 1402 [295342] provided by ActiveState http://www.ActiveSt +ate.com Built Oct 7 2011 15:19:36 Perl may be copied only under the terms of either the Artistic License + or the GNU General Public License, which may be found in the Perl 5 source ki +t. Complete documentation for Perl, including FAQ lists, should be found +on this system using "man perl" or "perldoc perl". If you have access to + the Internet, point your browser at http://www.perl.org/, the Perl Home Pa +ge. C:\> [download]	[reply] [d/l]
Re^3: IO::Pipe hangs by BrowserUk (Patriarch) on Sep 20, 2012 at 20:00 UTC
Something wrong with Windows implementation? More of a platform difference -- a thread used instead of a fork. Use this instead: `use strict; use warnings; my $cmd = "tasklist"; my $pid = open PIPE, "-\|", $cmd or die $!; while (my $line = <PIPE> ) { print $line; last if $line =~ /^smss/; } close PIPE;` [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' 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. RIP Neil Armstrong	[reply] [d/l]
Re^3: IO::Pipe hangs by Anonymous Monk on Sep 20, 2012 at 19:47 UTC
Something wrong with Windows implementation? It doesn't hang for me with sysinternals pslist, Devel::VersionDump `Perl version: v5.14.1 on MSWin32 (C:\perl\5.14.1\bin\MSWin32-x86-multi +-thread\perl.exe) Carp - 1.26 Devel::VersionDump - 0.02 Exporter - 5.66 IO - 1.25_04 IO::Handle - 1.31 IO::Pipe - 1.14 SelectSaver - 1.02 Symbol - 1.07 XSLoader - 0.15 strict - 1.04 warnings - 1.12` [download]	[reply] [d/l]