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Initial commit of OpenSPARC T2 architecture model.
[OpenSPARC-T2-SAM] / sam-t2 / devtools / v8plus / man / man3 / IPC::Open3.3
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129.\" ========================================================================
130.\"
131.IX Title "IPC::Open3 3"
132.TH IPC::Open3 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide"
133.SH "NAME"
134IPC::Open3, open3 \- open a process for reading, writing, and error handling
135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS"
137.Vb 2
138\& $pid = open3(\e*CHLD_IN, \e*CHLD_OUT, \e*CHLD_ERR,
139\& 'some cmd and args', 'optarg', ...);
140.Ve
141.PP
142.Vb 3
143\& my($wtr, $rdr, $err);
144\& $pid = open3($wtr, $rdr, $err,
145\& 'some cmd and args', 'optarg', ...);
146.Ve
147.SH "DESCRIPTION"
148.IX Header "DESCRIPTION"
149Extremely similar to \fIopen2()\fR, \fIopen3()\fR spawns the given \f(CW$cmd\fR and
150connects \s-1CHLD_OUT\s0 for reading from the child, \s-1CHLD_IN\s0 for writing to
151the child, and \s-1CHLD_ERR\s0 for errors. If \s-1CHLD_ERR\s0 is false, or the
152same file descriptor as \s-1CHLD_OUT\s0, then \s-1STDOUT\s0 and \s-1STDERR\s0 of the child
153are on the same filehandle. The \s-1CHLD_IN\s0 will have autoflush turned
154on.
155.PP
156If \s-1CHLD_IN\s0 begins with \f(CW\*(C`<&\*(C'\fR, then \s-1CHLD_IN\s0 will be closed in the
157parent, and the child will read from it directly. If \s-1CHLD_OUT\s0 or
158\&\s-1CHLD_ERR\s0 begins with \f(CW\*(C`>&\*(C'\fR, then the child will send output
159directly to that filehandle. In both cases, there will be a \fIdup\fR\|(2)
160instead of a \fIpipe\fR\|(2) made.
161.PP
162If either reader or writer is the null string, this will be replaced
163by an autogenerated filehandle. If so, you must pass a valid lvalue
164in the parameter slot so it can be overwritten in the caller, or
165an exception will be raised.
166.PP
167The filehandles may also be integers, in which case they are understood
168as file descriptors.
169.PP
170\&\fIopen3()\fR returns the process \s-1ID\s0 of the child process. It doesn't return on
171failure: it just raises an exception matching \f(CW\*(C`/^open3:/\*(C'\fR. However,
172\&\f(CW\*(C`exec\*(C'\fR failures in the child are not detected. You'll have to
173trap \s-1SIGPIPE\s0 yourself.
174.PP
175Note if you specify \f(CW\*(C`\-\*(C'\fR as the command, in an analogous fashion to
176\&\f(CW\*(C`open(FOO, "\-|")\*(C'\fR the child process will just be the forked Perl
177process rather than an external command. This feature isn't yet
178supported on Win32 platforms.
179.PP
180\&\fIopen3()\fR does not wait for and reap the child process after it exits.
181Except for short programs where it's acceptable to let the operating system
182take care of this, you need to do this yourself. This is normally as
183simple as calling \f(CW\*(C`waitpid $pid, 0\*(C'\fR when you're done with the process.
184Failing to do this can result in an accumulation of defunct or \*(L"zombie\*(R"
185processes. See \*(L"waitpid\*(R" in perlfunc for more information.
186.PP
187If you try to read from the child's stdout writer and their stderr
188writer, you'll have problems with blocking, which means you'll want
189to use \fIselect()\fR or the IO::Select, which means you'd best use
190\&\fIsysread()\fR instead of \fIreadline()\fR for normal stuff.
191.PP
192This is very dangerous, as you may block forever. It assumes it's
193going to talk to something like \fBbc\fR, both writing to it and reading
194from it. This is presumably safe because you \*(L"know\*(R" that commands
195like \fBbc\fR will read a line at a time and output a line at a time.
196Programs like \fBsort\fR that read their entire input stream first,
197however, are quite apt to cause deadlock.
198.PP
199The big problem with this approach is that if you don't have control
200over source code being run in the child process, you can't control
201what it does with pipe buffering. Thus you can't just open a pipe to
202\&\f(CW\*(C`cat \-v\*(C'\fR and continually read and write a line from it.
203.SH "WARNING"
204.IX Header "WARNING"
205The order of arguments differs from that of \fIopen2()\fR.
Full OpenSPARC architecture tarball including simulator, hypervisor, and OBP.