On Fri, Jan 23, 2009 at 11:11:45AM EST, Gerhard Siegesmund wrote: > Hello CJ > > I, for example, use the following script to monitor the number of > messages on my mailbox: > > ------------------------------------------------------------------------ > #!/bin/sh > > FETCHMAIL='/usr/bin/fetchmail' > > while true; do > $FETCHMAIL -c | sed -e 's/.* \([0-9]*\) messages* (\([0-9]*\) seen.*/\1 - > \2/g' | bc || exit 1 > sleep 60 > done > ------------------------------------------------------------------------ > > > I had the same problem as you. What fixed the problem was the '|| exit > 1'-Statement. > > The point is, when the terminal where the script writes to doesn't exist > anymore, then the outputting tool should signal this with an exitcode > other than 0. With '|| exit 1' in my example I check whether bc was able > to correctly output its result. If that was not possible, end the script > with 'exit 1'.
As I understand it correctly, it could still be "exit 0", right? What matters is the non-zero exit code from the pipe? Or does init need to be told that the child process ended with an ec^=0? Or even with precisely ec=1? > This way everytime my screen instance is killed, all the running > backtick-Scripts also end. Brilliant! And this just goes to show that understanding terminals is the first requirement of *nix programming. > Hope this helps. So much so that.. I'll forgive you for top-posting. ;-) Really, what a clever solution!!! As to others who replied, please don't fell slighted in any way. Your comments were also very useful: They made me realize that one other thing that doesn't make sense about my scripts is the "sleep" command. Maybe "sleep 60" or "sleep 1200" don't matter all that much - but having the linux kernel create a new address space every second just because I want my little script to go to sleep for one second.. and then a second later go through the motions of terminating a process that should not have been started in the first place.. sounds like a major waste of resources. Is there any way I could replace this by a system call or its library wrapper .. After all, what I really want is to tell the kernel not to dispatch my process for the next second or so. Why go about it in such a roundabout way by creating an empty subprocess that does nothing for one second? I'm no programmer.. so I hope the above makes sense. Humble as they are, these are monitoring tools .. I do want their impact on the system to be as neglibible as possible. Thanks, CJ _______________________________________________ screen-users mailing list screen-users@gnu.org http://lists.gnu.org/mailman/listinfo/screen-users
