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# &open3: Marc Horowitz <marc@mit.edu>
# derived mostly from &open2 by tom christiansen, <tchrist@convex.com>
#
# $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $
#
# usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...);
#
# spawn the given $cmd and connect rdr for
# reading, wtr for writing, and err for errors.
# if err is '', or the same as rdr, then stdout and
# stderr of the child are on the same fh. returns pid
# of child, or 0 on failure.
# if wtr begins with '>&', then wtr will be closed in the parent, and
# the child will read from it directly. if rdr or err begins with
# '>&', then the child will send output directly to that fd. In both
# cases, there will be a dup() instead of a pipe() made.
# WARNING: this is dangerous, as you may block forever
# unless you are very careful.
#
# $wtr is left unbuffered.
#
# abort program if
# rdr or wtr are null
# pipe or fork or exec fails
package open3;
$fh = 'FHOPEN000'; # package static in case called more than once
sub main'open3 {
local($kidpid);
local($dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
local($dup_wtr, $dup_rdr, $dup_err);
$dad_wtr || die "open3: wtr should not be null";
$dad_rdr || die "open3: rdr should not be null";
$dad_err = $dad_rdr if ($dad_err eq '');
$dup_wtr = ($dad_wtr =~ s/^\>\&//);
$dup_rdr = ($dad_rdr =~ s/^\>\&//);
$dup_err = ($dad_err =~ s/^\>\&//);
# force unqualified filehandles into callers' package
local($package) = caller;
$dad_wtr =~ s/^[^']+$/$package'$&/;
$dad_rdr =~ s/^[^']+$/$package'$&/;
$dad_err =~ s/^[^']+$/$package'$&/;
local($kid_rdr) = ++$fh;
local($kid_wtr) = ++$fh;
local($kid_err) = ++$fh;
if (!$dup_wtr) {
pipe($kid_rdr, $dad_wtr) || die "open3: pipe 1 (stdin) failed: $!";
}
if (!$dup_rdr) {
pipe($dad_rdr, $kid_wtr) || die "open3: pipe 2 (stdout) failed: $!";
}
if ($dad_err ne $dad_rdr && !$dup_err) {
pipe($dad_err, $kid_err) || die "open3: pipe 3 (stderr) failed: $!";
}
if (($kidpid = fork) < 0) {
die "open2: fork failed: $!";
} elsif ($kidpid == 0) {
if ($dup_wtr) {
open(STDIN, ">&$dad_wtr") if (fileno(STDIN) != fileno($dad_wtr));
} else {
close($dad_wtr);
open(STDIN, ">&$kid_rdr");
}
if ($dup_rdr) {
open(STDOUT, ">&$dad_rdr") if (fileno(STDOUT) != fileno($dad_rdr));
} else {
close($dad_rdr);
open(STDOUT, ">&$kid_wtr");
}
if ($dad_rdr ne $dad_err) {
if ($dup_err) {
open(STDERR, ">&$dad_err")
if (fileno(STDERR) != fileno($dad_err));
} else {
close($dad_err);
open(STDERR, ">&$kid_err");
}
} else {
open(STDERR, ">&STDOUT") if (fileno(STDERR) != fileno(STDOUT));
}
exec @cmd;
local($")=(" ");
die "open2: exec of @cmd failed";
}
close $kid_rdr; close $kid_wtr; close $kid_err;
if ($dup_wtr) {
close($dad_wtr);
}
select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe
$kidpid;
}
1; # so require is happy
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