On Sun, Feb 08, 2009 at 05:52:34PM +1000, Adrian Levi <adrian.l...@gmail.com> was heard to say: > 2009/2/8 Daniel Burrows <dburr...@debian.org>: > > Hello list, > > > > I've been banging my head on this one for a while. > > > > I have a need to write some code that can manage job control on a > > terminal. More specifically, I need to run a single process and stuff > > it into the background at will, so that it gets suspended when it tries > > to read from the terminal. So, there's a "controller" process and > > a "subprocess" process. > > > > controller ----------> subprocess > > manages > > You cant send the equivalent of ^z then fg to resume? > AFAIK the process will be suspended until you type bg to run the > process in the background or fg to bring it back into the foreground.
Well, the issue is that I don't know when to sent the SIGSTOP (that is, ^Z). :-) I'm trying to do it only when the process wants to read from the terminal, but allow it to run unmolested otherwise. Based on some additional tests I ran, it looks like the mechanism that triggers SIGTTIN only activates when the subprocess actually invokes the read() system call -- the one I was testing with blocks in select() until input is available, and that doesn't seem to trigger the TTIN. (if I type a character while it's "in the background", that does cause it to suspend) The use case here is basically that I have a hidden terminal with a long-running batch process that occasionally prompts for user input, and I want to detect when it's waiting so I can alert the user. I'm trying to find a way to get it to emit some sort of signal / event that the parent process can catch, and I latched onto SIGTTIN as a route to that. It's looking to me like it might not be possible to implement what I want through the job control mechanism, although I found some intriguing notes about VDSUSP yesterday that I haven't followed up on. Daniel -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
