There are several ways to find out whether a Unix or Linux process is running or not. Here are some options:
ps: The ps command displays information about the currently running processes on the system. You can use the -ef options to list all processes, along with their process IDs (PIDs) and command names.For example, to list all running processes on the system, you can use the following command:
ps -ef
This will display a list of all processes, along with their PIDs and command names. You can use the grep command to search for a specific process by its command name.
For example, to find out whether the process httpd (the Apache HTTP server daemon) is running, you can use the following command:
ps -ef | grep httpd
This will search the output of ps -ef for the string httpd and display any matching processes. If the process is running, it will be listed in the output. If the process is not running, the output will be empty.
pgrep: The pgrep command searches for processes by their command name and displays the PIDs of the matching processes.For example, to find out whether the process httpd is running, you can use the following command:
pgrep httpd
This will search for processes with the command name httpd and display the PIDs of the matching processes. If the process is running, the PID will be displayed. If the process is not running, the output will be empty.
pidof: The pidof command displays the PID of a running process.For example, to find the PID of the process httpd, you can use the following command:
pidof httpd
This will display the PID of the httpd process. If the process is not running, the output will be empty.