This is an exercise in finding and terminating processes running in the background.
In future assignments, you will implement programs that fork a lot, and you will make mistakes resulting in child processes continuing to run behind your back. If this happens on Mathlab or a lab computer, you are slowing down computers that other people need, and you are not being a good citizen! It is important that you find and terminate these runaway processes.
To practice this, compile and run the provided imtrash.c program. What it does: fork 5 children, then exit; but the children are still running! (In this lab, the children idle for 20 minutes then exit, no harm done in case you fail this mission. In reality, mistakes will likely cause children to actively hog the CPUs forever.)
Your jobs:
Keep in mind that a lot of other students may have similarly named processes too (when everyone is doing the same assignment on the same server). You must find and terminate those belonging to you only.
What to hand in: Write down your command(s) and/or method(s) in a text file cleanup.txt and submit it. It will be marked by a TA.
This is an exercise in launching a child process and setting up file redirection.
We will be implementing the equivalent of “cmd 2> filename”.
The finished program err-redir will take 2 or more arguments:
filename, program to run, command line arguments for that program. Example:
./err-redir xyz ls dneruns
ls dne, and its stderr should go to filename xyz.
(Since dne does not exist, there should be an error message in xyz.)
The provided starter file err-redir.c already has a skeleton. But there are many things to complete or fix (marked by “TODO”); please see the file for specifications.
Some sample programs are provided: sample (shell script) and check-open.c. Please take a look at what they do and how they help you test.
But here are some sample sessions:
$ ./err-redir xyz ls dne wait status: 0200 exit status: 2 $ cat xyz ls: cannot access 'dne': No such file or directory $ ./err-redir xyz ./sample 7 wait status: 0700 exit status: 7 $ cat xyz hi $ ./err-redir xyz ./sample signal wait status: 000f signal: 15 $ ./err-redir xyz ./sample po total 0 lrwx------ 1 trebla trebla 64 Jul 9 14:27 0 -> /dev/pts/0 lrwx------ 1 trebla trebla 64 Jul 9 14:27 1 -> /dev/pts/0 lrwx------ 1 trebla trebla 64 Jul 9 14:27 2 -> /dev/pts/0 wait status: 0000 exit status: 0 $ ./err-redir xyz ./check-open AOK wait status: 0000 exit status: 0 $ ./err-redir xyz ./err-redir.c cannot exec: Permission denied wait status: 7e00 exit status: 126 $ ./err-redir xyz asdfqwerty cannot exec: No such file or directory wait status: 7f00 exit status: 127