use IPC::Open2; $pid = open2(\*RDR, \*WTR, 'some cmd and args'); # or $pid = open2(\*RDR, \*WTR, 'some', 'cmd', 'and', 'args');
open2()function spawns the given
$rdrfor reading and
$wtrfor writing. It's what you think should work when you try
open(HANDLE, "|cmd args|");
The write filehandle will have autoflush turned on.
$rdr is a string (that is, a bareword filehandle rather than a glob or a reference) and it begins with ``>&'', then the child will send output directly to that file handle. If
$wtr is a string that begins with ``<&'', then
WTR will be closed in the parent, and the child will read from it directly. In both cases, there will be a
dup(2) instead of a
open2() returns the process
ID of the child process. It doesn't return on failure:
it just raises an exception matching
Additionally, this is very dangerous as you may block forever. It assumes it's going to talk to something like bc, both writing to it and reading from it. This is presumably safe because you ``know'' that commands like bc will read a line at a time and output a line at a time. Programs like sort that read their entire input stream first, however, are quite apt to cause deadlock.
The big problem with this approach is that if you don't have control over
source code being run in the child process, you can't control what it does
with pipe buffering. Thus you can't just open a pipe to
cat -v and continually read and write a line from it.