4 no strict 'refs'; # because users pass me bareword filehandles
5 our ($VERSION, @ISA, @EXPORT);
10 use Symbol qw(gensym qualify);
18 IPC::Open3, open3 - open a process for reading, writing, and error handling
22 $pid = open3(\*CHLD_IN, \*CHLD_OUT, \*CHLD_ERR,
23 'some cmd and args', 'optarg', ...);
26 $pid = open3($wtr, $rdr, $err,
27 'some cmd and args', 'optarg', ...);
30 my $child_exit_status = $? >> 8;
34 Extremely similar to open2(), open3() spawns the given $cmd and
35 connects CHLD_OUT for reading from the child, CHLD_IN for writing to
36 the child, and CHLD_ERR for errors. If CHLD_ERR is false, or the
37 same file descriptor as CHLD_OUT, then STDOUT and STDERR of the child
38 are on the same filehandle. The CHLD_IN will have autoflush turned
41 If CHLD_IN begins with C<< <& >>, then CHLD_IN will be closed in the
42 parent, and the child will read from it directly. If CHLD_OUT or
43 CHLD_ERR begins with C<< >& >>, then the child will send output
44 directly to that filehandle. In both cases, there will be a dup(2)
45 instead of a pipe(2) made.
47 If either reader or writer is the null string, this will be replaced
48 by an autogenerated filehandle. If so, you must pass a valid lvalue
49 in the parameter slot so it can be overwritten in the caller, or
50 an exception will be raised.
52 The filehandles may also be integers, in which case they are understood
55 open3() returns the process ID of the child process. It doesn't return on
56 failure: it just raises an exception matching C</^open3:/>. However,
57 C<exec> failures in the child (such as no such file or permission denied),
58 are just reported to CHLD_ERR, as it is not possible to trap them.
60 If the child process dies for any reason, the next write to CHLD_IN is
61 likely to generate a SIGPIPE in the parent, which is fatal by default.
62 So you may wish to handle this signal.
64 Note if you specify C<-> as the command, in an analogous fashion to
65 C<open(FOO, "-|")> the child process will just be the forked Perl
66 process rather than an external command. This feature isn't yet
67 supported on Win32 platforms.
69 open3() does not wait for and reap the child process after it exits.
70 Except for short programs where it's acceptable to let the operating system
71 take care of this, you need to do this yourself. This is normally as
72 simple as calling C<waitpid $pid, 0> when you're done with the process.
73 Failing to do this can result in an accumulation of defunct or "zombie"
74 processes. See L<perlfunc/waitpid> for more information.
76 If you try to read from the child's stdout writer and their stderr
77 writer, you'll have problems with blocking, which means you'll want
78 to use select() or the IO::Select, which means you'd best use
79 sysread() instead of readline() for normal stuff.
81 This is very dangerous, as you may block forever. It assumes it's
82 going to talk to something like B<bc>, both writing to it and reading
83 from it. This is presumably safe because you "know" that commands
84 like B<bc> will read a line at a time and output a line at a time.
85 Programs like B<sort> that read their entire input stream first,
86 however, are quite apt to cause deadlock.
88 The big problem with this approach is that if you don't have control
89 over source code being run in the child process, you can't control
90 what it does with pipe buffering. Thus you can't just open a pipe to
91 C<cat -v> and continually read and write a line from it.
99 Like Open3 but without STDERR catpure.
103 This is a CPAN module that has better error handling and more facilities
110 The order of arguments differs from that of open2().
114 # &open3: Marc Horowitz <marc@mit.edu>
115 # derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
116 # fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com>
117 # ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career
118 # fixed for autovivving FHs, tchrist again
119 # allow fd numbers to be used, by Frank Tobin
120 # allow '-' as command (c.f. open "-|"), by Adam Spiers <perl@adamspiers.org>
122 # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
124 # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
126 # spawn the given $cmd and connect rdr for
127 # reading, wtr for writing, and err for errors.
128 # if err is '', or the same as rdr, then stdout and
129 # stderr of the child are on the same fh. returns pid
130 # of child (or dies on failure).
133 # if wtr begins with '<&', then wtr will be closed in the parent, and
134 # the child will read from it directly. if rdr or err begins with
135 # '>&', then the child will send output directly to that fd. In both
136 # cases, there will be a dup() instead of a pipe() made.
139 # WARNING: this is dangerous, as you may block forever
140 # unless you are very careful.
142 # $wtr is left unbuffered.
145 # rdr or wtr are null
146 # a system call fails
148 our $Me = 'open3 (bug)'; # you should never see this, it's always localized
150 # Fatal.pm needs to be fixed WRT prototypes.
154 defined $pid or croak "$Me: fork failed: $!";
159 pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!";
162 # I tried using a * prototype character for the filehandle but it still
163 # disallows a bearword while compiling under strict subs.
166 open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!";
170 close $_[0] or croak "$Me: close($_[0]) failed: $!";
174 return $_[0] =~ /\A=?(\d+)\z/;
178 return $1 if $_[0] =~ /\A=?(\d+)\z/; # deal with fh just being an fd
182 my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32';
186 my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
187 my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
189 if (@cmd > 1 and $cmd[0] eq '-') {
190 croak "Arguments don't make sense when the command is '-'"
193 # simulate autovivification of filehandles because
194 # it's too ugly to use @_ throughout to make perl do it for us
198 $dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr;
199 $dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr;
202 # must strip crud for croak to add back, or looks ugly
203 $@ =~ s/(?<=value attempted) at .*//s;
207 $dad_err ||= $dad_rdr;
209 $dup_wtr = ($dad_wtr =~ s/^[<>]&//);
210 $dup_rdr = ($dad_rdr =~ s/^[<>]&//);
211 $dup_err = ($dad_err =~ s/^[<>]&//);
213 # force unqualified filehandles into caller's package
214 $dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr);
215 $dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr);
216 $dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err);
218 my $kid_rdr = gensym;
219 my $kid_wtr = gensym;
220 my $kid_err = gensym;
222 xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
223 xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
224 xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
226 $kidpid = $do_spawn ? -1 : xfork;
227 if ($kidpid == 0) { # Kid
228 # A tie in the parent should not be allowed to cause problems.
231 # If she wants to dup the kid's stderr onto her stdout I need to
232 # save a copy of her stdout before I put something else there.
233 if ($dad_rdr ne $dad_err && $dup_err
234 && xfileno($dad_err) == fileno(STDOUT)) {
236 xopen($tmp, ">&$dad_err");
241 xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr);
244 xopen \*STDIN, "<&=" . fileno $kid_rdr;
247 xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr);
250 xopen \*STDOUT, ">&=" . fileno $kid_wtr;
252 if ($dad_rdr ne $dad_err) {
254 # I have to use a fileno here because in this one case
255 # I'm doing a dup but the filehandle might be a reference
256 # (from the special case above).
257 xopen \*STDERR, ">&" . xfileno($dad_err)
258 if fileno(STDERR) != xfileno($dad_err);
261 xopen \*STDERR, ">&=" . fileno $kid_err;
264 xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
266 return 0 if ($cmd[0] eq '-');
269 carp "$Me: exec of @cmd failed";
270 eval { require POSIX; POSIX::_exit(255); };
273 } elsif ($do_spawn) {
274 # All the bookkeeping of coincidence between handles is
275 # handled in spawn_with_handles.
279 $kid_rdr = \*{$dad_wtr};
280 push @close, $kid_rdr;
282 push @close, \*{$dad_wtr}, $kid_rdr;
285 $kid_wtr = \*{$dad_rdr};
286 push @close, $kid_wtr;
288 push @close, \*{$dad_rdr}, $kid_wtr;
290 if ($dad_rdr ne $dad_err) {
292 $kid_err = \*{$dad_err};
293 push @close, $kid_err;
295 push @close, \*{$dad_err}, $kid_err;
302 spawn_with_handles( [ { mode => 'r',
307 handle => \*STDOUT },
310 handle => \*STDERR },
316 xclose $kid_rdr if !$dup_wtr;
317 xclose $kid_wtr if !$dup_rdr;
318 xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
319 # If the write handle is a dup give it away entirely, close my copy
321 xclose $dad_wtr if $dup_wtr;
323 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
330 croak "open3(@_): not enough arguments";
332 return _open3 'open3', scalar caller, @_
335 sub spawn_with_handles {
336 my $fds = shift; # Fields: handle, mode, open_as
337 my $close_in_child = shift;
338 my ($fd, $pid, @saved_fh, $saved, %saved, @errs);
341 foreach $fd (@$fds) {
342 $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode});
343 $saved{fileno $fd->{handle}} = $fd->{tmp_copy};
345 foreach $fd (@$fds) {
346 bless $fd->{handle}, 'IO::Handle'
347 unless eval { $fd->{handle}->isa('IO::Handle') } ;
348 # If some of handles to redirect-to coincide with handles to
349 # redirect, we need to use saved variants:
350 $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as},
353 unless ($^O eq 'MSWin32') {
354 # Stderr may be redirected below, so we save the err text:
355 foreach $fd (@$close_in_child) {
356 fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!"
357 unless $saved{fileno $fd}; # Do not close what we redirect!
362 $pid = eval { system 1, @_ }; # 1 == P_NOWAIT
363 push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0;
366 foreach $fd (@$fds) {
367 $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode});
368 $fd->{tmp_copy}->close or croak "Can't close: $!";
370 croak join "\n", @errs if @errs;
374 1; # so require is happy