9 # &open3: Marc Horowitz <marc@mit.edu>
10 # derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
12 # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
14 # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
16 # spawn the given $cmd and connect rdr for
17 # reading, wtr for writing, and err for errors.
18 # if err is '', or the same as rdr, then stdout and
19 # stderr of the child are on the same fh. returns pid
20 # of child, or 0 on failure.
23 # if wtr begins with '>&', then wtr will be closed in the parent, and
24 # the child will read from it directly. if rdr or err begins with
25 # '>&', then the child will send output directly to that fd. In both
26 # cases, there will be a dup() instead of a pipe() made.
29 # WARNING: this is dangerous, as you may block forever
30 # unless you are very careful.
32 # $wtr is left unbuffered.
36 # pipe or fork or exec fails
38 $fh = 'FHOPEN000'; # package static in case called more than once
42 local($dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
43 local($dup_wtr, $dup_rdr, $dup_err);
45 $dad_wtr || croak "open3: wtr should not be null";
46 $dad_rdr || croak "open3: rdr should not be null";
47 $dad_err = $dad_rdr if ($dad_err eq '');
49 $dup_wtr = ($dad_wtr =~ s/^\>\&//);
50 $dup_rdr = ($dad_rdr =~ s/^\>\&//);
51 $dup_err = ($dad_err =~ s/^\>\&//);
53 # force unqualified filehandles into callers' package
54 local($package) = caller;
55 $dad_wtr =~ s/^[^']+$/$package'$&/;
56 $dad_rdr =~ s/^[^']+$/$package'$&/;
57 $dad_err =~ s/^[^']+$/$package'$&/;
59 local($kid_rdr) = ++$fh;
60 local($kid_wtr) = ++$fh;
61 local($kid_err) = ++$fh;
64 pipe($kid_rdr, $dad_wtr) || croak "open3: pipe 1 (stdin) failed: $!";
67 pipe($dad_rdr, $kid_wtr) || croak "open3: pipe 2 (stdout) failed: $!";
69 if ($dad_err ne $dad_rdr && !$dup_err) {
70 pipe($dad_err, $kid_err) || croak "open3: pipe 3 (stderr) failed: $!";
73 if (($kidpid = fork) < 0) {
74 croak "open2: fork failed: $!";
75 } elsif ($kidpid == 0) {
77 open(STDIN, ">&$dad_wtr") if (fileno(STDIN) != fileno($dad_wtr));
80 open(STDIN, ">&$kid_rdr");
83 open(STDOUT, ">&$dad_rdr") if (fileno(STDOUT) != fileno($dad_rdr));
86 open(STDOUT, ">&$kid_wtr");
88 if ($dad_rdr ne $dad_err) {
90 open(STDERR, ">&$dad_err")
91 if (fileno(STDERR) != fileno($dad_err));
94 open(STDERR, ">&$kid_err");
97 open(STDERR, ">&STDOUT") if (fileno(STDERR) != fileno(STDOUT));
101 croak "open2: exec of @cmd failed";
104 close $kid_rdr; close $kid_wtr; close $kid_err;
109 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
112 1; # so require is happy