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.
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. In both
36 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 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>
70 # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
72 # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
74 # spawn the given $cmd and connect rdr for
75 # reading, wtr for writing, and err for errors.
76 # if err is '', or the same as rdr, then stdout and
77 # stderr of the child are on the same fh. returns pid
78 # of child (or dies on failure).
81 # if wtr begins with '<&', then wtr will be closed in the parent, and
82 # the child will read from it directly. if rdr or err begins with
83 # '>&', then the child will send output directly to that fd. In both
84 # cases, there will be a dup() instead of a pipe() made.
87 # WARNING: this is dangerous, as you may block forever
88 # unless you are very careful.
90 # $wtr is left unbuffered.
96 $Fh = 'FHOPEN000'; # package static in case called more than once
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: $!";
124 my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
125 my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
127 $dad_wtr or croak "$Me: wtr should not be null";
128 $dad_rdr or croak "$Me: rdr should not be null";
129 $dad_err = $dad_rdr if ($dad_err eq '');
131 $dup_wtr = ($dad_wtr =~ s/^[<>]&//);
132 $dup_rdr = ($dad_rdr =~ s/^[<>]&//);
133 $dup_err = ($dad_err =~ s/^[<>]&//);
135 # force unqualified filehandles into callers' package
136 $dad_wtr = qualify $dad_wtr, $package;
137 $dad_rdr = qualify $dad_rdr, $package;
138 $dad_err = qualify $dad_err, $package;
144 xpipe $kid_rdr, $dad_wtr if !$dup_wtr;
145 xpipe $dad_rdr, $kid_wtr if !$dup_rdr;
146 xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr;
150 # If she wants to dup the kid's stderr onto her stdout I need to
151 # save a copy of her stdout before I put something else there.
152 if ($dad_rdr ne $dad_err && $dup_err
153 && fileno($dad_err) == fileno(STDOUT)) {
155 xopen($tmp, ">&$dad_err");
160 open(STDIN, "<&$dad_wtr") if (fileno(STDIN) != fileno($dad_wtr));
163 open(STDIN, "<&$kid_rdr");
166 open(STDOUT, ">&$dad_rdr") if (fileno(STDOUT) != fileno($dad_rdr));
169 open(STDOUT, ">&$kid_wtr");
171 if ($dad_rdr ne $dad_err) {
173 open(STDERR, ">&$dad_err")
174 if (fileno(STDERR) != fileno($dad_err));
177 open(STDERR, ">&$kid_err");
180 open(STDERR, ">&STDOUT") if (fileno(STDERR) != fileno(STDOUT));
184 or croak "open3: exec of @cmd failed";
187 xclose $kid_rdr if !$dup_wtr;
188 xclose $kid_wtr if !$dup_rdr;
189 xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err;
190 # If the write handle is a dup give it away entirely, close my copy
192 xclose $dad_wtr if $dup_wtr;
194 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
199 return _open3 'open3', scalar caller, @_
201 1; # so require is happy