1 files changed, 47 insertions, 16 deletions
diff --git a/vest/line_mediator.pl b/vest/line_mediator.pl
index 5ae13aa4..f3c6dbf1 100755
--- a/vest/line_mediator.pl
+++ b/vest/line_mediator.pl
@@ -7,6 +7,8 @@
 
 use strict;
 use IPC::Open2;
+use POSIX qw(pipe dup2 STDIN_FILENO STDOUT_FILENO);
+#use IO::Handle;
 $,=' ';
 my $quiet=$ENV{QUIET};
 sub info {
@@ -14,24 +16,53 @@ sub info {
 }
 
 my @c1;
-do {
-    push @c1,shift
-} while $c1[$#c1] ne '--';
+if (scalar @ARGV) {
+    do {
+        push @c1,shift
+    } while $c1[$#c1] ne '--';
+}
 pop @c1;
 my @c2=@ARGV;
-(scalar @c1 && scalar @c2) || die "usage: $0 cmd1 args -- cmd2 args; hooks up two processes, 2nd of which has one line of output per line of input, expected by the first, which starts off the communication.  crosses stdin/stderr of cmd1 and cmd2 line by line (both must flush on newline and output.  cmd1 initiates the conversation (sends the first line).  QUIET env var suppresses debugging output.";
+(scalar @c1 && scalar @c2) || die "usage: $0 cmd1 args -- cmd2 args; hooks up two processes, 2nd of which has one line of output per line of input, expected by the first, which starts off the communication.  crosses stdin/stderr of cmd1 and cmd2 line by line (both must flush on newline and output.  cmd1 initiates the conversation (sends the first line).  QUIET=1 env var suppresses debugging output.  default: attempts to cross stdin/stdout of c1 and c2 directly (via two unidirectional posix pipes created before fork).  env SERIAL=1: (no parallelism possible) but lines exchanged are logged unless QUIET.";
+
 info("1 cmd:",@c1,"\n");
 info("2 cmd:",@c2,"\n");
-my ($R1,$W1,$R2,$W2);
-my $c1p=open2($R1,$W1,@c1); # Open2 R W backward from Open3.
-my $c2p=open2($R2,$W2,@c2);
-select $W2;
-$|=1;
-while(<$R1>) {
-    info("1:",$_);
-    print $_;
-    $_=<$R2>;
-    last unless defined $_;
-    info("2:",$_);
-    print $W1 $_;
+
+if ($ENV{SERIAL}) {
+    my ($R1,$W1,$R2,$W2);
+    my $c1p=open2($R1,$W1,@c1); # Open2 R W backward from Open3.
+    my $c2p=open2($R2,$W2,@c2);
+    select $W2;
+    $|=1;
+    while(<$R1>) {
+        info("1:",$_);
+        print $_;
+        $_=<$R2>;
+        last unless defined $_;
+        info("2:",$_);
+        print $W1 $_;
+    }
+} else {
+    my @rw1=POSIX::pipe();
+    my @rw2=POSIX::pipe();
+    my $pid=undef;
+    $SIG{CHLD} = sub { wait };
+#    close STDIN;
+#    close STDOUT;
+    while (not defined ($pid=fork())) {
+        sleep 1;
+    }
+#    info(STDOUT_FILENO,STDIN_FILENO,"\n");
+    POSIX::close(STDOUT_FILENO);
+    POSIX::close(STDIN_FILENO);
+    if ($pid) {
+        POSIX::dup2($rw1[1],STDOUT_FILENO);
+        POSIX::dup2($rw2[0],STDIN_FILENO);
+        exec @c1;
+    } else {
+        POSIX::dup2($rw2[1],STDOUT_FILENO);
+        POSIX::dup2($rw1[0],STDIN_FILENO);
+        exec @c2;
+    }
+    while (wait()!=-1) {}
 }