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RedHat 9 (Linux i386) - man page for ipc::open3 (redhat section 3pm)

IPC::Open3(3pm) 		 Perl Programmers Reference Guide		  IPC::Open3(3pm)

NAME
       IPC::Open3, open3 - open a process for reading, writing, and error handling

SYNOPSIS
	   $pid = open3(\*WTRFH, \*RDRFH, \*ERRFH,
			   'some cmd and args', 'optarg', ...);

	   my($wtr, $rdr, $err);
	   $pid = open3($wtr, $rdr, $err,
			   'some cmd and args', 'optarg', ...);

DESCRIPTION
       Extremely similar to open2(), open3() spawns the given $cmd and connects RDRFH for read-
       ing, WTRFH for writing, and ERRFH for errors.  If ERRFH is false, or the same file
       descriptor as RDRFH, then STDOUT and STDERR of the child are on the same filehandle.  The
       WTRFH will have autoflush turned on.

       If WTRFH begins with "<&", then WTRFH will be closed in the parent, and the child will
       read from it directly.  If RDRFH or ERRFH begins with ">&", then the child will send out-
       put directly to that filehandle.  In both cases, there will be a dup(2) instead of a
       pipe(2) made.

       If either reader or writer is the null string, this will be replaced by an autogenerated
       filehandle.  If so, you must pass a valid lvalue in the parameter slot so it can be over-
       written in the caller, or an exception will be raised.

       The filehandles may also be integers, in which case they are understood as file descrip-
       tors.

       open3() returns the process ID of the child process.  It doesn't return on failure: it
       just raises an exception matching "/^open3:/".  However, "exec" failures in the child are
       not detected.  You'll have to trap SIGPIPE yourself.

       open3() does not wait for and 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 the process.  Failing to do this can result in an accumulation of defunct or
       "zombie" processes.  See "waitpid" in perlfunc for more information.

       If you try to read from the child's stdout writer and their stderr writer, you'll have
       problems with blocking, which means you'll want to use select() or the IO::Select, which
       means you'd best use sysread() instead of readline() for normal stuff.

       This is very dangerous, as you may block forever.  It assumes it's going to talk to some-
       thing 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.

WARNING
       The order of arguments differs from that of open2().

perl v5.8.0				    2002-06-01				  IPC::Open3(3pm)


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