IPC::Open3(3) Perl Programmers Reference Guide IPC::Open3(3)NAME
IPC::Open3, open3 - open a process for reading, writing,
and error handling
SYNOPSIS
$pid = open3(\*WTRFH, \*RDRFH, \*ERRFH,
'some cmd and args', 'optarg', ...);
DESCRIPTION
Extremely similar to open2(), open3() spawns the given
$cmd and connects RDRFH for reading, WTRFH for writing,
and ERRFH for errors. If ERRFH is '', or the same as
RDRFH, then STDOUT and STDERR of the child are on the same
file handle. 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
output directly to that file handle. In both cases, there
will be a dup(2) instead of a pipe(2) made.
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(), which means
you'll have to use sysread() instead of normal stuff.
open3() returns the process ID of the child process. It
doesn't return on failure: it just raises an exception
matching /^open3:/.
WARNING
It will not create these file handles for you. You have
to do this yourself. So don't pass it empty variables
expecting them to get filled in for you.
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.
16/Sep/1999 perl 5.005, patch 03 1
IPC::Open3(3) Perl Programmers Reference Guide IPC::Open3(3)16/Sep/1999 perl 5.005, patch 03 2
