4 no strict 'refs'; # because users pass me bareword filehandles
5 use vars qw($VERSION @ISA @EXPORT $Fh $Me);
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 $Fh = 'FHOPEN000'; # package static in case called more than once
98 $Me = 'open3 (bug)'; # you should never see this, it's always localized
100 # Fatal.pm needs to be fixed WRT prototypes.
104 defined $pid or croak "$Me: fork failed: $!";
109 pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!";
112 # I tried using a * prototype character for the filehandle but it still
113 # disallows a bearword while compiling under strict subs.
116 open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!";
120 close $_[0] or croak "$Me: close($_[0]) failed: $!";
123 my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32';
127 my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
128 my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
130 $dad_wtr or croak "$Me: wtr should not be null";
131 $dad_rdr or croak "$Me: rdr should not be null";
132 $dad_err = $dad_rdr if ($dad_err eq '');
134 $dup_wtr = ($dad_wtr =~ s/^[<>]&//);
135 $dup_rdr = ($dad_rdr =~ s/^[<>]&//);
136 $dup_err = ($dad_err =~ s/^[<>]&//);
138 # force unqualified filehandles into callers' package
139 $dad_wtr = qualify $dad_wtr, $package;
140 $dad_rdr = qualify $dad_rdr, $package;
141 $dad_err = qualify $dad_err, $package;
147 xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
148 xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
149 xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
151 $kidpid = $do_spawn ? -1 : xfork;
152 if ($kidpid == 0) { # Kid
153 # If she wants to dup the kid's stderr onto her stdout I need to
154 # save a copy of her stdout before I put something else there.
155 if ($dad_rdr ne $dad_err && $dup_err
156 && fileno($dad_err) == fileno(STDOUT)) {
158 xopen($tmp, ">&$dad_err");
163 xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != fileno($dad_wtr);
166 xopen \*STDIN, "<&$kid_rdr";
170 xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != fileno($dad_rdr);
173 xopen \*STDOUT, ">&$kid_wtr";
176 if ($dad_rdr ne $dad_err) {
178 xopen \*STDERR, ">&$dad_err"
179 if fileno(STDERR) != fileno($dad_err);
182 xopen \*STDERR, ">&$kid_err";
186 xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
190 or croak "$Me: exec of @cmd failed";
191 } elsif ($do_spawn) {
192 # All the bookkeeping of coincidence between handles is
193 # handled in spawn_with_handles.
198 push @close, \*{$kid_rdr};
200 push @close, \*{$dad_wtr}, \*{$kid_rdr};
204 push @close, \*{$kid_wtr};
206 push @close, \*{$dad_rdr}, \*{$kid_wtr};
208 if ($dad_rdr ne $dad_err) {
210 $kid_err = $dad_err ;
211 push @close, \*{$kid_err};
213 push @close, \*{$dad_err}, \*{$kid_err};
220 spawn_with_handles( [ { mode => 'r',
221 open_as => \*{$kid_rdr},
224 open_as => \*{$kid_wtr},
225 handle => \*STDOUT },
227 open_as => \*{$kid_err},
228 handle => \*STDERR },
234 xclose $kid_rdr if !$dup_wtr;
235 xclose $kid_wtr if !$dup_rdr;
236 xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
237 # If the write handle is a dup give it away entirely, close my copy
239 xclose $dad_wtr if $dup_wtr;
241 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
248 croak "open3(@_): not enough arguments";
250 return _open3 'open3', scalar caller, @_
253 sub spawn_with_handles {
254 my $fds = shift; # Fields: handle, mode, open_as
255 my $close_in_child = shift;
256 my ($fd, $pid, @saved_fh, $saved, %saved, @errs);
259 foreach $fd (@$fds) {
260 $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode});
261 $saved{fileno $fd->{handle}} = $fd->{tmp_copy};
263 foreach $fd (@$fds) {
264 bless $fd->{handle}, 'IO::Handle'
265 unless eval { $fd->{handle}->isa('IO::Handle') } ;
266 # If some of handles to redirect-to coincide with handles to
267 # redirect, we need to use saved variants:
268 $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as},
271 unless ($^O eq 'MSWin32') {
272 # Stderr may be redirected below, so we save the err text:
273 foreach $fd (@$close_in_child) {
274 fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!"
275 unless $saved{fileno $fd}; # Do not close what we redirect!
280 $pid = eval { system 1, @_ }; # 1 == P_NOWAIT
281 push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0;
284 foreach $fd (@$fds) {
285 $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode});
286 $fd->{tmp_copy}->close or croak "Can't close: $!";
288 croak join "\n", @errs if @errs;
292 1; # so require is happy