|
The ps
-ef command displays a full
listing of every process, including the Process ID (PID)
and its Parent Process ID (PPID). When trying to terminate a
program or release a hung terminal window, it may not be enough to
kill the process ID that is associated with the unresponsive
application. It may be necessary to kill the Parent of that process
and on rare occasions even the Parent of the Parent. It is important
to be able to look at a PID and PPID to be able to trace from the
child up the hierarchy to the parent processes that spawned them.
To do this, you must first identify the
PID of the lowest level unresponsive process. Normally you would try
to kill that processes PID. If this does not stop the process, you may need to kill its parent. Killing a parent process will kill
all child processes spawned by it. It is also much quicker to kill a
parent process rather than killing perhaps several child processes.
The Figure shows three processes and the relationships between them.
In this example, the first process was started when the user opened a
terminal window from CDE, which spawned the user's opening a terminal
window for the default Korn shell (ksh). From there the user
opened a C Shell with the csh
command. Next they ran a program called sleep 500& which
suspends execution for 500 seconds. The ampersand (&) tells
the shell to run the command in the background and return the shell
prompt so the user can continue working.
Note - The sleep
command is frequently used in shell scripts to cause the machine to
pause for a specified number of seconds before continuing on to the
next command. It is used in this example only for purposes of
illustration.
The ps
-f command in the Figure is
used to see only those processes initiated from the current terminal
window. The sleep process has a process id of 785 and its
parent process is 742, which is the PID of the C shell (csh).
If you terminate PID 742, you will also terminate 785. If you
terminate the PID of the Korn shell (ksh), which is 689, you will
terminate all processes.
|