Monitoring processes using ps

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

• To list the processes associated with our current Bash shell Terminal, enter the following command:

    $ ps  

• To list processes, along with the parent process ID associated with the current Terminal, enter the following command:

    $ ps -f

• 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

• 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 the system processes, enter the following command:

    $ ps -ef 

• The process names in [] are kernel threads. If you are interested in more options for 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 the following command:

    $ kill  pid_of_process_to_be_killed

• Many a time, if the process is not killed by the $ kill command, you may need to pass additional options 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 with the name of a process, instead of using the process ID, as follows:

    $ pkill command_name
    $ pkill sleep  

• Or:

    $ pkill  -9  command_name  

• To know more about various flags of kill, enter the 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.