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(\*WTRFH, \*RDRFH, \*ERRFH,
23 'some cmd and args', 'optarg', ...);
26 $pid = open3($wtr, $rdr, $err,
27 'some cmd and args', 'optarg', ...);
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
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.
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.
47 open3() returns the process ID of the child process. It doesn't return on
48 failure: it just raises an exception matching C</^open3:/>. However,
49 C<exec> failures in the child are not detected. You'll have to
50 trap SIGPIPE yourself.
52 open3() does not wait for and reap the child process after it exits.
53 Except for short programs where it's acceptable to let the operating system
54 take care of this, you need to do this yourself. This is normally as
55 simple as calling C<waitpid $pid, 0> when you're done with the process.
56 Failing to do this can result in an accumulation of defunct or "zombie"
57 processes. See L<perlfunc/waitpid> for more information.
59 If you try to read from the child's stdout writer and their stderr
60 writer, you'll have problems with blocking, which means you'll want
61 to use select() or the IO::Select, which means you'd best use
62 sysread() instead of readline() for normal stuff.
64 This is very dangerous, as you may block forever. It assumes it's
65 going to talk to something like B<bc>, both writing to it and reading
66 from it. This is presumably safe because you "know" that commands
67 like B<bc> will read a line at a time and output a line at a time.
68 Programs like B<sort> that read their entire input stream first,
69 however, are quite apt to cause deadlock.
71 The big problem with this approach is that if you don't have control
72 over source code being run in the child process, you can't control
73 what it does with pipe buffering. Thus you can't just open a pipe to
74 C<cat -v> and continually read and write a line from it.
78 The order of arguments differs from that of open2().
82 # &open3: Marc Horowitz <marc@mit.edu>
83 # derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
84 # fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com>
85 # ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career
86 # fixed for autovivving FHs, tchrist again
87 # allow fd numbers to be used, by Frank Tobin
89 # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
91 # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
93 # spawn the given $cmd and connect rdr for
94 # reading, wtr for writing, and err for errors.
95 # if err is '', or the same as rdr, then stdout and
96 # stderr of the child are on the same fh. returns pid
97 # of child (or dies on failure).
100 # if wtr begins with '<&', then wtr will be closed in the parent, and
101 # the child will read from it directly. if rdr or err begins with
102 # '>&', then the child will send output directly to that fd. In both
103 # cases, there will be a dup() instead of a pipe() made.
106 # WARNING: this is dangerous, as you may block forever
107 # unless you are very careful.
109 # $wtr is left unbuffered.
112 # rdr or wtr are null
113 # a system call fails
115 our $Me = 'open3 (bug)'; # you should never see this, it's always localized
117 # Fatal.pm needs to be fixed WRT prototypes.
121 defined $pid or croak "$Me: fork failed: $!";
126 pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!";
129 # I tried using a * prototype character for the filehandle but it still
130 # disallows a bearword while compiling under strict subs.
133 open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!";
137 close $_[0] or croak "$Me: close($_[0]) failed: $!";
142 return $1 if $fh =~ /^=?(\d+)$/; # deal with $fh just being an fd
147 return $_[0] =~ /^=?\d+$/;
150 my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32';
154 my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
155 my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
157 # simulate autovivification of filehandles because
158 # it's too ugly to use @_ throughout to make perl do it for us
162 $dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr;
163 $dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr;
166 # must strip crud for croak to add back, or looks ugly
167 $@ =~ s/(?<=value attempted) at .*//s;
171 $dad_err ||= $dad_rdr;
173 $dup_wtr = ($dad_wtr =~ s/^[<>]&//);
174 $dup_rdr = ($dad_rdr =~ s/^[<>]&//);
175 $dup_err = ($dad_err =~ s/^[<>]&//);
177 # force unqualified filehandles into caller's package
178 $dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr);
179 $dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr);
180 $dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err);
182 my $kid_rdr = gensym;
183 my $kid_wtr = gensym;
184 my $kid_err = gensym;
186 xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
187 xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
188 xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
190 $kidpid = $do_spawn ? -1 : xfork;
191 if ($kidpid == 0) { # Kid
192 # If she wants to dup the kid's stderr onto her stdout I need to
193 # save a copy of her stdout before I put something else there.
194 if ($dad_rdr ne $dad_err && $dup_err
195 && xfileno($dad_err) == fileno(STDOUT)) {
197 xopen($tmp, ">&$dad_err");
202 xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr);
205 xopen \*STDIN, "<&=" . fileno $kid_rdr;
208 xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr);
211 xopen \*STDOUT, ">&=" . fileno $kid_wtr;
213 if ($dad_rdr ne $dad_err) {
215 # I have to use a fileno here because in this one case
216 # I'm doing a dup but the filehandle might be a reference
217 # (from the special case above).
218 xopen \*STDERR, ">&" . xfileno($dad_err)
219 if fileno(STDERR) != xfileno($dad_err);
222 xopen \*STDERR, ">&=" . fileno $kid_err;
225 xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
228 exec @cmd # XXX: wrong process to croak from
229 or croak "$Me: exec of @cmd failed";
230 } elsif ($do_spawn) {
231 # All the bookkeeping of coincidence between handles is
232 # handled in spawn_with_handles.
236 $kid_rdr = \*{$dad_wtr};
237 push @close, $kid_rdr;
239 push @close, \*{$dad_wtr}, $kid_rdr;
242 $kid_wtr = \*{$dad_rdr};
243 push @close, $kid_wtr;
245 push @close, \*{$dad_rdr}, $kid_wtr;
247 if ($dad_rdr ne $dad_err) {
249 $kid_err = \*{$dad_err};
250 push @close, $kid_err;
252 push @close, \*{$dad_err}, $kid_err;
259 spawn_with_handles( [ { mode => 'r',
264 handle => \*STDOUT },
267 handle => \*STDERR },
273 xclose $kid_rdr if !$dup_wtr;
274 xclose $kid_wtr if !$dup_rdr;
275 xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
276 # If the write handle is a dup give it away entirely, close my copy
278 xclose $dad_wtr if $dup_wtr;
280 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
287 croak "open3(@_): not enough arguments";
289 return _open3 'open3', scalar caller, @_
292 sub spawn_with_handles {
293 my $fds = shift; # Fields: handle, mode, open_as
294 my $close_in_child = shift;
295 my ($fd, $pid, @saved_fh, $saved, %saved, @errs);
298 foreach $fd (@$fds) {
299 $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode});
300 $saved{fileno $fd->{handle}} = $fd->{tmp_copy};
302 foreach $fd (@$fds) {
303 bless $fd->{handle}, 'IO::Handle'
304 unless eval { $fd->{handle}->isa('IO::Handle') } ;
305 # If some of handles to redirect-to coincide with handles to
306 # redirect, we need to use saved variants:
307 $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as},
310 unless ($^O eq 'MSWin32') {
311 # Stderr may be redirected below, so we save the err text:
312 foreach $fd (@$close_in_child) {
313 fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!"
314 unless $saved{fileno $fd}; # Do not close what we redirect!
319 $pid = eval { system 1, @_ }; # 1 == P_NOWAIT
320 push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0;
323 foreach $fd (@$fds) {
324 $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode});
325 $fd->{tmp_copy}->close or croak "Can't close: $!";
327 croak join "\n", @errs if @errs;
331 1; # so require is happy