Initial Commit

database/perl/lib/IPC/Open2.pm

@@ -0,0 +1,124 @@
+package IPC::Open2;
+
+use strict;
+our ($VERSION, @ISA, @EXPORT);
+
+require 5.000;
+require Exporter;
+
+$VERSION	= 1.05;
+@ISA		= qw(Exporter);
+@EXPORT		= qw(open2);
+
+=head1 NAME
+
+IPC::Open2 - open a process for both reading and writing using open2()
+
+=head1 SYNOPSIS
+
+    use IPC::Open2;
+
+    my $pid = open2(my $chld_out, my $chld_in,
+      'some', 'cmd', 'and', 'args');
+    # or passing the command through the shell
+    my $pid = open2(my $chld_out, my $chld_in, 'some cmd and args');
+
+    # read from parent STDIN and write to already open handle
+    open my $outfile, '>', 'outfile.txt' or die "open failed: $!";
+    my $pid = open2($outfile, '<&STDIN', 'some', 'cmd', 'and', 'args');
+
+    # read from already open handle and write to parent STDOUT
+    open my $infile, '<', 'infile.txt' or die "open failed: $!";
+    my $pid = open2('>&STDOUT', $infile, 'some', 'cmd', 'and', 'args');
+
+    # reap zombie and retrieve exit status
+    waitpid( $pid, 0 );
+    my $child_exit_status = $? >> 8;
+
+=head1 DESCRIPTION
+
+The open2() function runs the given command and connects $chld_out for
+reading and $chld_in for writing.  It's what you think should work 
+when you try
+
+    my $pid = open(my $fh, "|cmd args|");
+
+The $chld_in filehandle will have autoflush turned on.
+
+If $chld_out is a string (that is, a bareword filehandle rather than a glob
+or a reference) and it begins with C<< >& >>, then the child will send output
+directly to that file handle.  If $chld_in is a string that begins with
+C<< <& >>, then $chld_in will be closed in the parent, and the child will
+read from it directly.  In both cases, there will be a L<dup(2)> instead of a
+L<pipe(2)> made.
+
+If either reader or writer is the empty string or undefined, this will be
+replaced by an autogenerated filehandle.  If so, you must pass a valid lvalue
+in the parameter slot so it can be overwritten in the caller, or
+an exception will be raised.
+
+open2() returns the process ID of the child process.  It doesn't return on
+failure: it just raises an exception matching C</^open2:/>.  However,
+C<exec> failures in the child are not detected.  You'll have to
+trap SIGPIPE yourself.
+
+open2() 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 C<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 L<perlfunc/waitpid> for more information.
+
+This whole affair is quite dangerous, as you may block forever.  It
+assumes it's going to talk to something like L<bc(1)>, both writing
+to it and reading from it.  This is presumably safe because you
+"know" that commands like L<bc(1)> will read a line at a time and
+output a line at a time.  Programs like L<sort(1)> 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
+C<cat -v> and continually read and write a line from it.
+
+The L<IO::Pty> and L<Expect> modules from CPAN can help with this, as
+they provide a real tty (well, a pseudo-tty, actually), which gets you
+back to line buffering in the invoked command again.
+
+=head1 WARNING 
+
+The order of arguments differs from that of open3().
+
+=head1 SEE ALSO
+
+See L<IPC::Open3> for an alternative that handles STDERR as well.  This
+function is really just a wrapper around open3().
+
+=cut
+
+# &open2: tom christiansen, <tchrist@convex.com>
+#
+# usage: $pid = open2('rdr', 'wtr', 'some cmd and args');
+#    or  $pid = open2('rdr', 'wtr', 'some', 'cmd', 'and', 'args');
+#
+# spawn the given $cmd and connect $rdr for
+# reading and $wtr for writing.  return pid
+# of child, or 0 on failure.  
+# 
+# WARNING: this is dangerous, as you may block forever
+# unless you are very careful.  
+# 
+# $wtr is left unbuffered.
+# 
+# abort program if
+#	rdr or wtr are null
+# 	a system call fails
+
+require IPC::Open3;
+
+sub open2 {
+    local $Carp::CarpLevel = $Carp::CarpLevel + 1;
+    return IPC::Open3::_open3('open2', $_[1], $_[0], '>&STDERR', @_[2 .. $#_]);
+}
+
+1