Re^2: How to know whether user terminates system("$cmd|more") with q or not?

[PerlOnTheWay]

You mentioned

watch STDIN in the separate thread, and let it watch for q

Will it work theoretically?

Say, will the thread be able to capture q if it's already consumed by more?

[zentara]

Will it work theoretically?Say, will the thread be able to capture q if it's already consumed by more?

Theoretically yes,I think your only way to do it that way is to somehow dup stdin. See

Found in /usr/lib/perl5/5.14.1/pod/perlfaq5.pod
   How do I dup() a filehandle in Perl?
   If you check "open" in perlfunc, you'll see that several of the way
+s to
       call open() should do the trick. For example:

               open my $log, '>>', '/foo/logfile';
               open STDERR, '>&LOG';

       Or even with a literal numeric descriptor:

               my $fd = $ENV{MHCONTEXTFD};
               open $mhcontext, "<&=$fd";  # like fdopen(3S)

       Note that "<&STDIN" makes a copy, but "<&=STDIN" makes an alias
+. That
       means if you close an aliased handle, all aliases become inacce
+ssible.
       This is not true with a copied one.

       Error checking, as always, has been left as an exercise for the
+ reader.

Then your stdin watcher thread and main thread might be able to both get the q . As with error checking, seeing if it works is left as an exercise to the OP. :-). Googling for "perl duping stdin" should give you some already written code.

But I think you are trying to do this the hard way, you probably would be better off putting your code into an eventloop of some sort, and using a piped open to run your $cmd.

[PerlOnTheWay]

What I want to run is not $cmd,but $cmd|more

[zentara]

I think you should describe exactly what you are trying to do, what $cmd you are running, and the whole big picture. Can you use a gui like Tk or does it have to be commandline?