Monitoring processes using ps

We have used the command ps in the introduction. Let's learn more about it:

  • To list the process associated with our current Bash shell terminal, enter the following command:
    $ ps
    Monitoring processes using ps
  • To list processes along with the parent process ID associated with the current terminal, enter the following command:
    $ ps –f
    Monitoring processes using ps

    We can see the process ID in the PID column and the parent process ID in the PPID column in the preceding output.

  • To list processes with the parent process ID along with the process state, enter the following command:
    $ ps –lf
    Monitoring processes using ps

    In the preceding output, the column with S (state) shows the current state of a process, such as R for running and S for suspended state.

  • To list all the processes running in the operating system including system processes, enter the following command:
    $ ps –ef
    Monitoring processes using ps

    The process names in [] are kernel threads. If you are interested in more options to learn about the ps command, you can use the following command:

    $ man ps.

    To find a particular process, you can use the following command:

    $ ps –ef | grep "process_name"

    The command with grep will display the process with process_name.

  • If we want to terminate the running process, enter following command:
    $ kill  pid_of_process_to_be_killed
    Monitoring processes using ps
  • Many a time, if the process is not killed by the $ kill command, you may need to pass additional option to ensure that the required process is killed, which is shown as follows:
    $ kill -9 pid_of_process_to_be_killed
  • We can terminate the process by the name of a process instead of using the process ID as follows:
    $ pkill command_name
$ pkill sleep

    Or:

    $ pkill  -9  command_name
    Monitoring processes using ps
  • To know more about various flags of kill, enter following command:
    $ kill –l

    This displays all the signals or software interrupts used by the operating system. When we enter the $ kill command, the operating system sends the SIGTERM signal to the process. If the process is not killed by this command, then we enter the following command:

    $ kill -9 process_name

    This sends SIGKILL to the process to be killed.

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