script/lei: background ourselves on MUA/pager exec

This ought to give the MUA or pager exclusive access to the
controlling terminal.  The downside is we can only exec the
pager or MUA once per invocation, but I can't imagine a valid
case for running those things multiple times, either.

Note: I'm no expert when it comes to terminal control matters,
but this allows Ctrl-Z-ed mutt instance to come back and is
a nice code reduction, as well.

1 files changed, 15 insertions, 22 deletions

diff --git a/script/lei b/script/lei
index cb605e2e..bea8dcde 100755
--- a/script/lei
+++ b/script/lei
@@ -14,36 +14,31 @@ my $send_cmd = PublicInbox::CmdIPC4->can('send_cmd4') // do {
         PublicInbox::Spawn->can('send_cmd4');
 };
 
-my %pids;
-my $sigchld = sub {
-        my $flags = scalar(@_) ? POSIX::WNOHANG() : 0;
-        for my $pid (keys %pids) {
-                delete($pids{$pid}) if waitpid($pid, $flags) == $pid;
-        }
-};
-
+my @orig_pid;
 my $exec_cmd = sub {
         my ($fds, $argc, @argv) = @_;
+        die "BUG: already exec-ed\n" if @orig_pid;
+        @orig_pid = ($$);
+        require POSIX; # WNOHANG
         my @old = (*STDIN{IO}, *STDOUT{IO}, *STDERR{IO});
         my @rdr;
         for my $fd (@$fds) {
                 open(my $tmpfh, '+<&=', $fd) or die "open +<&=$fd: $!";
                 push @rdr, shift(@old), $tmpfh;
         }
-        require POSIX; # WNOHANG
-        $SIG{CHLD} = $sigchld;
         my $pid = fork // die "fork: $!";
         if ($pid == 0) {
-                my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
-                while (my ($old_io, $tmpfh) = splice(@rdr, 0, 2)) {
-                        open $old_io, '+<&', $tmpfh or die "open +<&=: $!";
-                }
-                %ENV = (%ENV, %env);
-                exec(@argv);
-                warn "exec: @argv: $!\n";
-                POSIX::_exit(1);
+                POSIX::setsid() > 0 or die "setsid: $!";
+                return; # continue $recv_cmd in background
+        }
+        my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
+        while (my ($old_io, $tmpfh) = splice(@rdr, 0, 2)) {
+                open $old_io, '+<&', $tmpfh or die "open +<&=: $!";
         }
-        $pids{$pid} = 1;
+        @ENV{keys %env} = values %env;
+        exec(@argv);
+        warn "exec: @argv: $!\n";
+        POSIX::_exit(1);
 };
 
 if ($send_cmd && eval {
@@ -100,18 +95,16 @@ Falling back to (slow) one-shot mode
                 if ($buf =~ /\Aexec (.+)\z/) {
                         $exec_cmd->(\@fds, split(/\0/, $1));
                 } elsif ($buf eq '-WINCH') {
-                        kill($buf, $$); # for MUA
+                        kill($buf, @orig_pid); # for MUA
                 } elsif ($buf =~ /\Ax_it ([0-9]+)\z/) {
                         $x_it_code = $1 + 0;
                         last;
                 } elsif ($buf =~ /\Achild_error ([0-9]+)\z/) {
                         $x_it_code = $1 + 0;
                 } else {
-                        $sigchld->();
                         die $buf;
                 }
         }
-        $sigchld->();
         if (my $sig = ($x_it_code & 127)) {
                 kill $sig, $$;
                 sleep(1) while 1;