4 no strict 'refs'; # because users pass me bareword filehandles
5 use vars qw($VERSION @ISA @EXPORT $Me);
11 use Symbol qw(gensym qualify);
19 IPC::Open3, open3 - open a process for reading, writing, and error handling
23 $pid = open3(\*WTRFH, \*RDRFH, \*ERRFH,
24 'some cmd and args', 'optarg', ...);
28 Extremely similar to open2(), open3() spawns the given $cmd and
29 connects RDRFH for reading, WTRFH for writing, and ERRFH for errors. If
30 ERRFH is '', or the same as RDRFH, then STDOUT and STDERR of the child are
31 on the same file handle. The WTRFH will have autoflush turned on.
33 If WTRFH begins with "E<lt>&", then WTRFH will be closed in the parent, and
34 the child will read from it directly. If RDRFH or ERRFH begins with
35 "E<gt>&", then the child will send output directly to that file handle.
36 In both cases, there will be a dup(2) instead of a pipe(2) made.
38 If you try to read from the child's stdout writer and their stderr
39 writer, you'll have problems with blocking, which means you'll
40 want to use select(), which means you'll have to use sysread() instead
43 open3() returns the process ID of the child process. It doesn't return on
44 failure: it just raises an exception matching C</^open3:/>.
48 It will not create these file handles for you. You have to do this
49 yourself. So don't pass it empty variables expecting them to get filled
52 Additionally, this is very dangerous as you may block forever. It
53 assumes it's going to talk to something like B<bc>, both writing to it
54 and reading from it. This is presumably safe because you "know" that
55 commands like B<bc> will read a line at a time and output a line at a
56 time. Programs like B<sort> that read their entire input stream first,
57 however, are quite apt to cause deadlock.
59 The big problem with this approach is that if you don't have control
60 over source code being run in the child process, you can't control
61 what it does with pipe buffering. Thus you can't just open a pipe to
62 C<cat -v> and continually read and write a line from it.
66 # &open3: Marc Horowitz <marc@mit.edu>
67 # derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
68 # fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com>
69 # ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career
71 # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
73 # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
75 # spawn the given $cmd and connect rdr for
76 # reading, wtr for writing, and err for errors.
77 # if err is '', or the same as rdr, then stdout and
78 # stderr of the child are on the same fh. returns pid
79 # of child (or dies on failure).
82 # if wtr begins with '<&', then wtr will be closed in the parent, and
83 # the child will read from it directly. if rdr or err begins with
84 # '>&', then the child will send output directly to that fd. In both
85 # cases, there will be a dup() instead of a pipe() made.
88 # WARNING: this is dangerous, as you may block forever
89 # unless you are very careful.
91 # $wtr is left unbuffered.
97 $Me = 'open3 (bug)'; # you should never see this, it's always localized
99 # Fatal.pm needs to be fixed WRT prototypes.
103 defined $pid or croak "$Me: fork failed: $!";
108 pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!";
111 # I tried using a * prototype character for the filehandle but it still
112 # disallows a bearword while compiling under strict subs.
115 open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!";
119 close $_[0] or croak "$Me: close($_[0]) failed: $!";
122 my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32';
126 my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
127 my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
129 $dad_wtr or croak "$Me: wtr should not be null";
130 $dad_rdr or croak "$Me: rdr should not be null";
131 $dad_err = $dad_rdr if ($dad_err eq '');
133 $dup_wtr = ($dad_wtr =~ s/^[<>]&//);
134 $dup_rdr = ($dad_rdr =~ s/^[<>]&//);
135 $dup_err = ($dad_err =~ s/^[<>]&//);
137 # force unqualified filehandles into callers' package
138 $dad_wtr = qualify $dad_wtr, $package;
139 $dad_rdr = qualify $dad_rdr, $package;
140 $dad_err = qualify $dad_err, $package;
142 my $kid_rdr = gensym;
143 my $kid_wtr = gensym;
144 my $kid_err = gensym;
146 xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
147 xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
148 xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
150 $kidpid = $do_spawn ? -1 : xfork;
151 if ($kidpid == 0) { # Kid
152 # If she wants to dup the kid's stderr onto her stdout I need to
153 # save a copy of her stdout before I put something else there.
154 if ($dad_rdr ne $dad_err && $dup_err
155 && fileno($dad_err) == fileno(STDOUT)) {
157 xopen($tmp, ">&$dad_err");
162 xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != fileno($dad_wtr);
165 xopen \*STDIN, "<&=" . fileno $kid_rdr;
168 xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != fileno($dad_rdr);
171 xopen \*STDOUT, ">&=" . fileno $kid_wtr;
173 if ($dad_rdr ne $dad_err) {
175 # I have to use a fileno here because in this one case
176 # I'm doing a dup but the filehandle might be a reference
177 # (from the special case above).
178 xopen \*STDERR, ">&" . fileno $dad_err
179 if fileno(STDERR) != fileno($dad_err);
182 xopen \*STDERR, ">&=" . fileno $kid_err;
185 xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
189 or croak "$Me: exec of @cmd failed";
190 } elsif ($do_spawn) {
191 # All the bookkeeping of coincidence between handles is
192 # handled in spawn_with_handles.
196 $kid_rdr = \*{$dad_wtr};
197 push @close, $kid_rdr;
199 push @close, \*{$dad_wtr}, $kid_rdr;
202 $kid_wtr = \*{$dad_rdr};
203 push @close, $kid_wtr;
205 push @close, \*{$dad_rdr}, $kid_wtr;
207 if ($dad_rdr ne $dad_err) {
209 $kid_err = \*{$dad_err};
210 push @close, $kid_err;
212 push @close, \*{$dad_err}, $kid_err;
219 spawn_with_handles( [ { mode => 'r',
224 handle => \*STDOUT },
227 handle => \*STDERR },
233 xclose $kid_rdr if !$dup_wtr;
234 xclose $kid_wtr if !$dup_rdr;
235 xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
236 # If the write handle is a dup give it away entirely, close my copy
238 xclose $dad_wtr if $dup_wtr;
240 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
247 croak "open3(@_): not enough arguments";
249 return _open3 'open3', scalar caller, @_
252 sub spawn_with_handles {
253 my $fds = shift; # Fields: handle, mode, open_as
254 my $close_in_child = shift;
255 my ($fd, $pid, @saved_fh, $saved, %saved, @errs);
258 foreach $fd (@$fds) {
259 $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode});
260 $saved{fileno $fd->{handle}} = $fd->{tmp_copy};
262 foreach $fd (@$fds) {
263 bless $fd->{handle}, 'IO::Handle'
264 unless eval { $fd->{handle}->isa('IO::Handle') } ;
265 # If some of handles to redirect-to coincide with handles to
266 # redirect, we need to use saved variants:
267 $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as},
270 unless ($^O eq 'MSWin32') {
271 # Stderr may be redirected below, so we save the err text:
272 foreach $fd (@$close_in_child) {
273 fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!"
274 unless $saved{fileno $fd}; # Do not close what we redirect!
279 $pid = eval { system 1, @_ }; # 1 == P_NOWAIT
280 push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0;
283 foreach $fd (@$fds) {
284 $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode});
285 $fd->{tmp_copy}->close or croak "Can't close: $!";
287 croak join "\n", @errs if @errs;
291 1; # so require is happy