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.

diff --git a/script/lei b/script/lei
index cb605e2eac1dc7bf9259b84e95dc506e5e8df4d9..bea8dcde97ea1be5662f4a02803137ca981bafbb 100755 (executable)
--- 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;