lib/IPC/Open3.pm

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        = 1.0106;
@ISA            = qw(Exporter);
@EXPORT         = qw(open3);

=head1 NAME

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

=head1 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', ...);

=head1 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 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 C<< <& >>, then WTRFH will be closed in the parent, and
the child will read from it directly.  If RDRFH or ERRFH 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 are not detected.  You'll have to 
trap SIGPIPE yourself.

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 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];
}

my $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);

    # 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 $kid_err;
            }
        } else {
            xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
        }
        if ($cmd[0] eq '-') {
            croak "Arguments don't make sense when the command is '-'"
              if @cmd > 1;
            return 0;
        }
        local($")=(" ");
        exec @cmd # XXX: wrong process to croak from
            or croak "$Me: exec of @cmd failed";
    } 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
Revision:	1.1
Committed:	Thu Jun 30 14:27:12 2005 UTC (21 years, 4 months ago) by root
Branch:	MAIN
CVS Tags:	HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	Content
1	package IPC::Open3;
2
3	use strict;
4	no strict 'refs'; # because users pass me bareword filehandles
5	our ($VERSION, @ISA, @EXPORT);
6
7	require Exporter;
8
9	use Carp;
10	use Symbol qw(gensym qualify);
11
12	$VERSION = 1.0106;
13	@ISA = qw(Exporter);
14	@EXPORT = qw(open3);
15
16	=head1 NAME
17
18	IPC::Open3, open3 - open a process for reading, writing, and error handling
19
20	=head1 SYNOPSIS
21
22	$pid = open3(\WTRFH, \RDRFH, \*ERRFH,
23	'some cmd and args', 'optarg', ...);
24
25	my($wtr, $rdr, $err);
26	$pid = open3($wtr, $rdr, $err,
27	'some cmd and args', 'optarg', ...);
28
29	=head1 DESCRIPTION
30
31	Extremely similar to open2(), open3() spawns the given $cmd and
32	connects RDRFH for reading, WTRFH for writing, and ERRFH for errors. If
33	ERRFH is false, or the same file descriptor as RDRFH, then STDOUT and
34	STDERR of the child are on the same filehandle. The WTRFH will have
35	autoflush turned on.
36
37	If WTRFH begins with C<< <& >>, then WTRFH will be closed in the parent, and
38	the child will read from it directly. If RDRFH or ERRFH begins with
39	C<< >& >>, then the child will send output directly to that filehandle.
40	In both cases, there will be a dup(2) instead of a pipe(2) made.
41
42	If either reader or writer is the null string, this will be replaced
43	by an autogenerated filehandle. If so, you must pass a valid lvalue
44	in the parameter slot so it can be overwritten in the caller, or
45	an exception will be raised.
46
47	The filehandles may also be integers, in which case they are understood
48	as file descriptors.
49
50	open3() returns the process ID of the child process. It doesn't return on
51	failure: it just raises an exception matching C</^open3:/>. However,
52	C<exec> failures in the child are not detected. You'll have to
53	trap SIGPIPE yourself.
54
55	Note if you specify C<-> as the command, in an analogous fashion to
56	C<open(FOO, "-\|")> the child process will just be the forked Perl
57	process rather than an external command. This feature isn't yet
58	supported on Win32 platforms.
59
60	open3() does not wait for and reap the child process after it exits.
61	Except for short programs where it's acceptable to let the operating system
62	take care of this, you need to do this yourself. This is normally as
63	simple as calling C<waitpid $pid, 0> when you're done with the process.
64	Failing to do this can result in an accumulation of defunct or "zombie"
65	processes. See L<perlfunc/waitpid> for more information.
66
67	If you try to read from the child's stdout writer and their stderr
68	writer, you'll have problems with blocking, which means you'll want
69	to use select() or the IO::Select, which means you'd best use
70	sysread() instead of readline() for normal stuff.
71
72	This is very dangerous, as you may block forever. It assumes it's
73	going to talk to something like B<bc>, both writing to it and reading
74	from it. This is presumably safe because you "know" that commands
75	like B<bc> will read a line at a time and output a line at a time.
76	Programs like B<sort> that read their entire input stream first,
77	however, are quite apt to cause deadlock.
78
79	The big problem with this approach is that if you don't have control
80	over source code being run in the child process, you can't control
81	what it does with pipe buffering. Thus you can't just open a pipe to
82	C<cat -v> and continually read and write a line from it.
83
84	=head1 WARNING
85
86	The order of arguments differs from that of open2().
87
88	=cut
89
90	# &open3: Marc Horowitz <marc@mit.edu>
91	# derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
92	# fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com>
93	# ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career
94	# fixed for autovivving FHs, tchrist again
95	# allow fd numbers to be used, by Frank Tobin
96	# allow '-' as command (c.f. open "-\|"), by Adam Spiers <perl@adamspiers.org>
97	#
98	# $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
99	#
100	# usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
101	#
102	# spawn the given $cmd and connect rdr for
103	# reading, wtr for writing, and err for errors.
104	# if err is '', or the same as rdr, then stdout and
105	# stderr of the child are on the same fh. returns pid
106	# of child (or dies on failure).
107
108
109	# if wtr begins with '<&', then wtr will be closed in the parent, and
110	# the child will read from it directly. if rdr or err begins with
111	# '>&', then the child will send output directly to that fd. In both
112	# cases, there will be a dup() instead of a pipe() made.
113
114
115	# WARNING: this is dangerous, as you may block forever
116	# unless you are very careful.
117	#
118	# $wtr is left unbuffered.
119	#
120	# abort program if
121	# rdr or wtr are null
122	# a system call fails
123
124	our $Me = 'open3 (bug)'; # you should never see this, it's always localized
125
126	# Fatal.pm needs to be fixed WRT prototypes.
127
128	sub xfork {
129	my $pid = fork;
130	defined $pid or croak "$Me: fork failed: $!";
131	return $pid;
132	}
133
134	sub xpipe {
135	pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!";
136	}
137
138	# I tried using a * prototype character for the filehandle but it still
139	# disallows a bearword while compiling under strict subs.
140
141	sub xopen {
142	open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!";
143	}
144
145	sub xclose {
146	close $_[0] or croak "$Me: close($_[0]) failed: $!";
147	}
148
149	sub fh_is_fd {
150	return $_[0] =~ /\A=?(\d+)\z/;
151	}
152
153	sub xfileno {
154	return $1 if $_[0] =~ /\A=?(\d+)\z/; # deal with fh just being an fd
155	return fileno $_[0];
156	}
157
158	my $do_spawn = $^O eq 'os2' \|\| $^O eq 'MSWin32';
159
160	sub _open3 {
161	local $Me = shift;
162	my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
163	my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
164
165	# simulate autovivification of filehandles because
166	# it's too ugly to use @_ throughout to make perl do it for us
167	# tchrist 5-Mar-00
168
169	unless (eval {
170	$dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr;
171	$dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr;
172	1; })
173	{
174	# must strip crud for croak to add back, or looks ugly
175	$@ =~ s/(?<=value attempted) at .*//s;
176	croak "$Me: $@";
177	}
178
179	$dad_err \|\|= $dad_rdr;
180
181	$dup_wtr = ($dad_wtr =~ s/^[<>]&//);
182	$dup_rdr = ($dad_rdr =~ s/^[<>]&//);
183	$dup_err = ($dad_err =~ s/^[<>]&//);
184
185	# force unqualified filehandles into caller's package
186	$dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr);
187	$dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr);
188	$dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err);
189
190	my $kid_rdr = gensym;
191	my $kid_wtr = gensym;
192	my $kid_err = gensym;
193
194	xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
195	xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
196	xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
197
198	$kidpid = $do_spawn ? -1 : xfork;
199	if ($kidpid == 0) { # Kid
200	# A tie in the parent should not be allowed to cause problems.
201	untie *STDIN;
202	untie *STDOUT;
203	# If she wants to dup the kid's stderr onto her stdout I need to
204	# save a copy of her stdout before I put something else there.
205	if ($dad_rdr ne $dad_err && $dup_err
206	&& xfileno($dad_err) == fileno(STDOUT)) {
207	my $tmp = gensym;
208	xopen($tmp, ">&$dad_err");
209	$dad_err = $tmp;
210	}
211
212	if ($dup_wtr) {
213	xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr);
214	} else {
215	xclose $dad_wtr;
216	xopen \*STDIN, "<&=" . fileno $kid_rdr;
217	}
218	if ($dup_rdr) {
219	xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr);
220	} else {
221	xclose $dad_rdr;
222	xopen \*STDOUT, ">&=" . fileno $kid_wtr;
223	}
224	if ($dad_rdr ne $dad_err) {
225	if ($dup_err) {
226	# I have to use a fileno here because in this one case
227	# I'm doing a dup but the filehandle might be a reference
228	# (from the special case above).
229	xopen \*STDERR, ">&" . xfileno($dad_err)
230	if fileno(STDERR) != xfileno($dad_err);
231	} else {
232	xclose $dad_err;
233	xopen \*STDERR, ">&=" . fileno $kid_err;
234	}
235	} else {
236	xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
237	}
238	if ($cmd[0] eq '-') {
239	croak "Arguments don't make sense when the command is '-'"
240	if @cmd > 1;
241	return 0;
242	}
243	local($")=(" ");
244	exec @cmd # XXX: wrong process to croak from
245	or croak "$Me: exec of @cmd failed";
246	} elsif ($do_spawn) {
247	# All the bookkeeping of coincidence between handles is
248	# handled in spawn_with_handles.
249
250	my @close;
251	if ($dup_wtr) {
252	$kid_rdr = \*{$dad_wtr};
253	push @close, $kid_rdr;
254	} else {
255	push @close, \*{$dad_wtr}, $kid_rdr;
256	}
257	if ($dup_rdr) {
258	$kid_wtr = \*{$dad_rdr};
259	push @close, $kid_wtr;
260	} else {
261	push @close, \*{$dad_rdr}, $kid_wtr;
262	}
263	if ($dad_rdr ne $dad_err) {
264	if ($dup_err) {
265	$kid_err = \*{$dad_err};
266	push @close, $kid_err;
267	} else {
268	push @close, \*{$dad_err}, $kid_err;
269	}
270	} else {
271	$kid_err = $kid_wtr;
272	}
273	require IO::Pipe;
274	$kidpid = eval {
275	spawn_with_handles( [ { mode => 'r',
276	open_as => $kid_rdr,
277	handle => \*STDIN },
278	{ mode => 'w',
279	open_as => $kid_wtr,
280	handle => \*STDOUT },
281	{ mode => 'w',
282	open_as => $kid_err,
283	handle => \*STDERR },
284	], \@close, @cmd);
285	};
286	die "$Me: $@" if $@;
287	}
288
289	xclose $kid_rdr if !$dup_wtr;
290	xclose $kid_wtr if !$dup_rdr;
291	xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
292	# If the write handle is a dup give it away entirely, close my copy
293	# of it.
294	xclose $dad_wtr if $dup_wtr;
295
296	select((select($dad_wtr), $\| = 1)[0]); # unbuffer pipe
297	$kidpid;
298	}
299
300	sub open3 {
301	if (@_ < 4) {
302	local $" = ', ';
303	croak "open3(@_): not enough arguments";
304	}
305	return _open3 'open3', scalar caller, @_
306	}
307
308	sub spawn_with_handles {
309	my $fds = shift; # Fields: handle, mode, open_as
310	my $close_in_child = shift;
311	my ($fd, $pid, @saved_fh, $saved, %saved, @errs);
312	require Fcntl;
313
314	foreach $fd (@$fds) {
315	$fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode});
316	$saved{fileno $fd->{handle}} = $fd->{tmp_copy};
317	}
318	foreach $fd (@$fds) {
319	bless $fd->{handle}, 'IO::Handle'
320	unless eval { $fd->{handle}->isa('IO::Handle') } ;
321	# If some of handles to redirect-to coincide with handles to
322	# redirect, we need to use saved variants:
323	$fd->{handle}->fdopen($saved{fileno $fd->{open_as}} \|\| $fd->{open_as},
324	$fd->{mode});
325	}
326	unless ($^O eq 'MSWin32') {
327	# Stderr may be redirected below, so we save the err text:
328	foreach $fd (@$close_in_child) {
329	fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!"
330	unless $saved{fileno $fd}; # Do not close what we redirect!
331	}
332	}
333
334	unless (@errs) {
335	$pid = eval { system 1, @_ }; # 1 == P_NOWAIT
336	push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid \|\| $pid < 0;
337	}
338
339	foreach $fd (@$fds) {
340	$fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode});
341	$fd->{tmp_copy}->close or croak "Can't close: $!";
342	}
343	croak join "\n", @errs if @errs;
344	return $pid;
345	}
346
347	1; # so require is happy