My fifo wtf.

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

Is there a reason why IPC::Open2 doesn't work with fifos, or am I doing something wrong.

These two examples must be run in different ttys, or you must background the echo to foobar, because it will wait for the output to be read before echo detaches.

mkfifo foobar;
echo "this is a test of the emergency fifo system" > foobar;
[download]

use IPC::Open2;
open(my $fifo, "<", "foobar") or die $!;
my $o; open(my $fh, ">", \$o) or die $!;
open2($fh, $fifo, "/bin/echo") or die $!;
print $o;
[download]

Evan Carroll
I hack for the ladies.
www.EvanCarroll.com

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Re: My fifo wtf. by ikegami (Patriarch) on Dec 18, 2008 at 03:12 UTC
You want `cat` (which echos its STDIN) for the child process, not `echo` (which echos its args). Update: Added "for the child process" as per reply.	[reply] [d/l] [select]
Re^2: My fifo wtf. by Mr. Muskrat (Canon) on Dec 18, 2008 at 16:58 UTC
You should have specified that it is the second `echo` that should be replaced by `cat`.	[reply]
Re: My fifo wtf. by ikegami (Patriarch) on Dec 18, 2008 at 03:16 UTC
Also, `open \$var` doesn't create a system file handle, just a Perl handle. It can't become the child's STDOUT.	[reply] [d/l]
Re^2: My fifo wtf. by EvanCarroll (Chaplain) on Dec 18, 2008 at 18:45 UTC
So how do you capture STDOUT from the child into perl? Evan Carroll I hack for the ladies. www.EvanCarroll.com	[reply]
Re^3: My fifo wtf. by ikegami (Patriarch) on Dec 18, 2008 at 19:15 UTC
`open(my $from_child, '-\|', "cat < foobar") or die $!; <$from_child>` [download] `open2(my $from_child, $fifo, "cat") or die $!; <$from_child>` [download]	[reply] [d/l] [select]