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32.30. IPC::Open2
use IPC::Open2;
local(*HIS_OUT, *HIS_IN); # Create local handles if needed.
$childpid = open2(*HIS_OUT, *HIS_IN, $program, @args)
or die "can't open pipe to $program: $!";
print HIS_IN "here's your input\n";
$his_output = <HIS_IN>;
close(HIS_OUT);
close(README);
waitpid($childpid, 0);
The IPC::Open2 module's one exported function, open2, starts
up another program and provides both read and write access to that command.
The first two arguments should be valid filehandles (or else empty
variables into which autogenerated filehandles can be placed). The
remaining arguments are the program plus its arguments, which if
passed in separately will not be subject to shell interpolation.
This module does not reap the child process after it exits. Except for
short programs where it's acceptable to let the operating system
take care of this, you need to do this yourself. This is normally
as simple as calling waitpid $pid, 0 when you're done with that
child process. Failure to do this can result in an accumulation
of defunct ("zombie") processes.In practice, this module doesn't work well with many programs because
of the way buffering works in C's standard I/O library. If you
control the source code to both programs, however, you can easily
circumvent this restriction by flushing your output buffers more
frequently than the default. If you don't, programs can be annoyingly
miserly in their hoarding of output. Another potential pitfall is
deadlock: if both processes are reading at the same time, and no
one is writing, then your program will hang. See Chapter 16, "Interprocess Communication" for more discussion.