Re: [TUHS] Sockets and the true UNIX

Kulp's name (and IIASA) appeared in several source files, I think; I know I came across them. Job control is a little overly complicated but there's only one really big mistake in it, in my opinion, and that is that the process group IDs are not allocated in the kernel. This is what led to all the "session group leader" cruft in POSIX. Job control ought to be independent of tty devices: each shell pipeline is a "job", and the shell should group them by having the kernel create an initial empty(ish -- the shell is a member of both its original pgroup and this one it just created, until it detaches from it) job, then pushing each process it forks into that pgroup. I'll use "fd" as a name here since I think that's one way to return them (they're refcounted like file descriptors) but not the only way, and it probably makes more sense to return a pgroup ID directly and have a pgclose()... // in a shell: fd = new_pgroup(); // kernel allocates pgroup for (all commands in a pipeline) { pid = fork(); if (pid == 0) { // child pid = getpid(); setpgrp(pid, fd); ... all the other stuff we do ... exec(childprocess) } if (pid < 0) ... clean up ... // still in the shell - set up the rest of the pipe using // the same pgroup } close(fd); // we're done with the pgroup, it goes away // when the last pid we created above also exits Note that this would mean that anything that creates login sessions would have to have this same kind of code (create a pgroup, fork, push child into pgroup, exec shell). But that's already true for job control in general: init or getty needs to be job-control-aware, and this makes their code simpler. Chris