Exploring Processes Exercises
- Examining Processes
- Examine the processes you are currently running on your machine. View these several
different ways using different flags (e.g. -x, -f, -u and combinations of these). Note these
flags may behave differently based upon the specific Unix shell you are using. Make sure you
understand most major groupings, such as process name, PID, PPID, STAT, etc. in each different view.
- Create a new process that will remain running, e.g. start a bash shell (bash). Now examine your
processes as you did above and notice what has changed. Display the STAT information and explain
what each letter indicates for each process.
- Terminate the shell process you just started and view your processes as above. Notice the PID for
your original shell is the same, but the PID for the ps command is different. Can you explain this?
- Examine all of the processes currently running on your system and display with PID and PPID
(try the flags -eaf). Locate your bottom-most (newest) process. Once finding this, follow this
process up the process hierarchy via PPIDs until the top-most process is reached. Before actually doing
this, what should the name of the top-most process be? Make sure you understand what each process is in
your process tree.
- Now use the pstree command to view your processes. Examine your process hierarchy and relate
this to the step above, displayed in a different format.
- Practice the above until you are sure you are comfortable with and understand these tasks.
- Overlaying Processes
- Examine (and make note of) the process information for the shell you are currently running.
- Now use the exec command to overlay your current process with a different shell (e.g.
- Once complete, examine your process status again, noting the newly overlayed process
as well as the PID of this process. Make sure you understand what happened and why?
- Terminating Processes
- Create two windows and login into your Unix machine via both.
- Use the ps command to view all of your processes, including both login sessions (e.g. -x flag).
Make note of both shell processes, and try to determine which shell is running in
which window. This may be done by time stamp, PID, or you may need to use the tty command.
- Set focus to one of the terminal windows and use the kill command to terminate the login
connection in the other. What process do you need to kill to terminate the login connection?
- Make sure you understand what happened and why?.
©2003-2004, Mark A. Thomas. All Rights Reserved.