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+package IPC::Open3;
+
+use strict;
+no strict 'refs'; # because users pass me bareword filehandles
+our ($VERSION, @ISA, @EXPORT);
+
+require Exporter;
+
+use Carp;
+use Symbol qw(gensym qualify);
+
+$VERSION = 1.05;
+@ISA = qw(Exporter);
+@EXPORT = qw(open3);
+
+=head1 NAME
+
+IPC::Open3 - open a process for reading, writing, and error handling using open3()
+
+=head1 SYNOPSIS
+
+ $pid = open3(\*CHLD_IN, \*CHLD_OUT, \*CHLD_ERR,
+ 'some cmd and args', 'optarg', ...);
+
+ my($wtr, $rdr, $err);
+ use Symbol 'gensym'; $err = gensym;
+ $pid = open3($wtr, $rdr, $err,
+ 'some cmd and args', 'optarg', ...);
+
+ waitpid( $pid, 0 );
+ my $child_exit_status = $? >> 8;
+
+=head1 DESCRIPTION
+
+Extremely similar to open2(), open3() spawns the given $cmd and
+connects CHLD_OUT for reading from the child, CHLD_IN for writing to
+the child, and CHLD_ERR for errors. If CHLD_ERR is false, or the
+same file descriptor as CHLD_OUT, then STDOUT and STDERR of the child
+are on the same filehandle (this means that an autovivified lexical
+cannot be used for the STDERR filehandle, see SYNOPSIS). The CHLD_IN
+will have autoflush turned on.
+
+If CHLD_IN begins with C<< <& >>, then CHLD_IN will be closed in the
+parent, and the child will read from it directly. If CHLD_OUT or
+CHLD_ERR begins with C<< >& >>, then the child will send output
+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 overwritten in the caller, or
+an exception will be raised.
+
+The filehandles may also be integers, in which case they are understood
+as file descriptors.
+
+open3() returns the process ID of the child process. It doesn't return on
+failure: it just raises an exception matching C</^open3:/>. However,
+C<exec> failures in the child (such as no such file or permission denied),
+are just reported to CHLD_ERR, as it is not possible to trap them.
+
+If the child process dies for any reason, the next write to CHLD_IN is
+likely to generate a SIGPIPE in the parent, which is fatal by default.
+So you may wish to handle this signal.
+
+Note if you specify C<-> as the command, in an analogous fashion to
+C<open(FOO, "-|")> the child process will just be the forked Perl
+process rather than an external command. This feature isn't yet
+supported on Win32 platforms.
+
+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 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.
+
+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 something like B<bc>, both writing to it and reading
+from it. This is presumably safe because you "know" that commands
+like B<bc> will read a line at a time and output a line at a time.
+Programs like B<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
+C<cat -v> and continually read and write a line from it.
+
+=head1 See Also
+
+=over 4
+
+=item L<IPC::Open2>
+
+Like Open3 but without STDERR catpure.
+
+=item L<IPC::Run>
+
+This is a CPAN module that has better error handling and more facilities
+than Open3.
+
+=back
+
+=head1 WARNING
+
+The order of arguments differs from that of open2().
+
+=cut
+
+# &open3: Marc Horowitz <marc@mit.edu>
+# derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
+# fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com>
+# ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career
+# fixed for autovivving FHs, tchrist again
+# allow fd numbers to be used, by Frank Tobin
+# allow '-' as command (c.f. open "-|"), by Adam Spiers <perl@adamspiers.org>
+#
+# $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
+#
+# usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
+#
+# spawn the given $cmd and connect rdr for
+# reading, wtr for writing, and err for errors.
+# if err is '', or the same as rdr, then stdout and
+# stderr of the child are on the same fh. returns pid
+# of child (or dies on failure).
+
+
+# if wtr begins with '<&', then wtr will be closed in the parent, and
+# the child will read from it directly. if rdr or err begins with
+# '>&', then the child will send output directly to that fd. In both
+# cases, there will be a dup() instead of a pipe() made.
+
+
+# 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
+
+our $Me = 'open3 (bug)'; # you should never see this, it's always localized
+
+# Fatal.pm needs to be fixed WRT prototypes.
+
+sub xfork {
+ my $pid = fork;
+ defined $pid or croak "$Me: fork failed: $!";
+ return $pid;
+}
+
+sub xpipe {
+ pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!";
+}
+
+# I tried using a * prototype character for the filehandle but it still
+# disallows a bearword while compiling under strict subs.
+
+sub xopen {
+ open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!";
+}
+
+sub xclose {
+ close $_[0] or croak "$Me: close($_[0]) failed: $!";
+}
+
+sub fh_is_fd {
+ return $_[0] =~ /\A=?(\d+)\z/;
+}
+
+sub xfileno {
+ return $1 if $_[0] =~ /\A=?(\d+)\z/; # deal with fh just being an fd
+ return fileno $_[0];
+}
+
+use constant DO_SPAWN => $^O eq 'os2' || $^O eq 'MSWin32';
+
+sub _open3 {
+ local $Me = shift;
+ my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
+ my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
+
+ if (@cmd > 1 and $cmd[0] eq '-') {
+ croak "Arguments don't make sense when the command is '-'"
+ }
+
+ # simulate autovivification of filehandles because
+ # it's too ugly to use @_ throughout to make perl do it for us
+ # tchrist 5-Mar-00
+
+ unless (eval {
+ $dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr;
+ $dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr;
+ 1; })
+ {
+ # must strip crud for croak to add back, or looks ugly
+ $@ =~ s/(?<=value attempted) at .*//s;
+ croak "$Me: $@";
+ }
+
+ $dad_err ||= $dad_rdr;
+
+ $dup_wtr = ($dad_wtr =~ s/^[<>]&//);
+ $dup_rdr = ($dad_rdr =~ s/^[<>]&//);
+ $dup_err = ($dad_err =~ s/^[<>]&//);
+
+ # force unqualified filehandles into caller's package
+ $dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr);
+ $dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr);
+ $dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err);
+
+ my $kid_rdr = gensym;
+ my $kid_wtr = gensym;
+ my $kid_err = gensym;
+
+ xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
+ xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
+ xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
+
+ $kidpid = DO_SPAWN ? -1 : xfork;
+ if ($kidpid == 0) { # Kid
+ # A tie in the parent should not be allowed to cause problems.
+ untie *STDIN;
+ untie *STDOUT;
+ # If she wants to dup the kid's stderr onto her stdout I need to
+ # save a copy of her stdout before I put something else there.
+ if ($dad_rdr ne $dad_err && $dup_err
+ && xfileno($dad_err) == fileno(STDOUT)) {
+ my $tmp = gensym;
+ xopen($tmp, ">&$dad_err");
+ $dad_err = $tmp;
+ }
+
+ if ($dup_wtr) {
+ xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr);
+ } else {
+ xclose $dad_wtr;
+ xopen \*STDIN, "<&=" . fileno $kid_rdr;
+ }
+ if ($dup_rdr) {
+ xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr);
+ } else {
+ xclose $dad_rdr;
+ xopen \*STDOUT, ">&=" . fileno $kid_wtr;
+ }
+ if ($dad_rdr ne $dad_err) {
+ if ($dup_err) {
+ # I have to use a fileno here because in this one case
+ # I'm doing a dup but the filehandle might be a reference
+ # (from the special case above).
+ xopen \*STDERR, ">&" . xfileno($dad_err)
+ if fileno(STDERR) != xfileno($dad_err);
+ } else {
+ xclose $dad_err;
+ xopen \*STDERR, ">&=" . fileno $kid_err;
+ }
+ } else {
+ xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
+ }
+ return 0 if ($cmd[0] eq '-');
+ local($")=(" ");
+ exec @cmd or do {
+ carp "$Me: exec of @cmd failed";
+ eval { require POSIX; POSIX::_exit(255); };
+ exit 255;
+ };
+ } elsif (DO_SPAWN) {
+ # All the bookkeeping of coincidence between handles is
+ # handled in spawn_with_handles.
+
+ my @close;
+ if ($dup_wtr) {
+ $kid_rdr = \*{$dad_wtr};
+ push @close, $kid_rdr;
+ } else {
+ push @close, \*{$dad_wtr}, $kid_rdr;
+ }
+ if ($dup_rdr) {
+ $kid_wtr = \*{$dad_rdr};
+ push @close, $kid_wtr;
+ } else {
+ push @close, \*{$dad_rdr}, $kid_wtr;
+ }
+ if ($dad_rdr ne $dad_err) {
+ if ($dup_err) {
+ $kid_err = \*{$dad_err};
+ push @close, $kid_err;
+ } else {
+ push @close, \*{$dad_err}, $kid_err;
+ }
+ } else {
+ $kid_err = $kid_wtr;
+ }
+ require IO::Pipe;
+ $kidpid = eval {
+ spawn_with_handles( [ { mode => 'r',
+ open_as => $kid_rdr,
+ handle => \*STDIN },
+ { mode => 'w',
+ open_as => $kid_wtr,
+ handle => \*STDOUT },
+ { mode => 'w',
+ open_as => $kid_err,
+ handle => \*STDERR },
+ ], \@close, @cmd);
+ };
+ die "$Me: $@" if $@;
+ }
+
+ xclose $kid_rdr if !$dup_wtr;
+ xclose $kid_wtr if !$dup_rdr;
+ xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
+ # If the write handle is a dup give it away entirely, close my copy
+ # of it.
+ xclose $dad_wtr if $dup_wtr;
+
+ select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
+ $kidpid;
+}
+
+sub open3 {
+ if (@_ < 4) {
+ local $" = ', ';
+ croak "open3(@_): not enough arguments";
+ }
+ return _open3 'open3', scalar caller, @_
+}
+
+sub spawn_with_handles {
+ my $fds = shift; # Fields: handle, mode, open_as
+ my $close_in_child = shift;
+ my ($fd, $pid, @saved_fh, $saved, %saved, @errs);
+ require Fcntl;
+
+ foreach $fd (@$fds) {
+ $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode});
+ $saved{fileno $fd->{handle}} = $fd->{tmp_copy};
+ }
+ foreach $fd (@$fds) {
+ bless $fd->{handle}, 'IO::Handle'
+ unless eval { $fd->{handle}->isa('IO::Handle') } ;
+ # If some of handles to redirect-to coincide with handles to
+ # redirect, we need to use saved variants:
+ $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as},
+ $fd->{mode});
+ }
+ unless ($^O eq 'MSWin32') {
+ # Stderr may be redirected below, so we save the err text:
+ foreach $fd (@$close_in_child) {
+ fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!"
+ unless $saved{fileno $fd}; # Do not close what we redirect!
+ }
+ }
+
+ unless (@errs) {
+ $pid = eval { system 1, @_ }; # 1 == P_NOWAIT
+ push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0;
+ }
+
+ foreach $fd (@$fds) {
+ $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode});
+ $fd->{tmp_copy}->close or croak "Can't close: $!";
+ }
+ croak join "\n", @errs if @errs;
+ return $pid;
+}
+
+1; # so require is happy