How to Find PID of a Linux Process With pidof or pgrep

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Linux manages its running processes internally by assigning each one a distinct ID number, referred to as the process ID, or PID. A PID is assigned to each active programme, utility, and daemon. Simple integer values make up PIDs. A freshly launched process will be assigned a PID that is one higher than the previous PID. Therefore, the most recent—that is, most recently launched—process is the one with the highest PID. This continues until the PID’s maximum value is reached by the system.

A PID can have a maximum value of 32768. When that number is reached, Linux starts over and searches for a PID that is now available since a process that was previously its owner has ended. When Linux is started by the boot-up processes, the process with a PID of 1 is the first to run. That will be systemd on systems running systemd. On other systems, init is probably the default, while some Linux versions also utilize OpenRc or s6 as alternatives. We mentioned below are the ways to Find PID of a Linux Process With pidof or pgrep.

Ways to Find PID of a Linux Process With pidof or pgrep

Find out process pid is running or not on your Linux

Simply use ps command command as follows:

ps aux | grep {process-name-here}ps -aux | grep {process-to-find-here}

For example, let us find out if mysqld process (mysqld pid) is running or not. Type:

$ ps aux | grep mysqld

The grep command act as filter. The | is called a shell pipe. It is a way to connect the output of one program to the input of another program without any temporary file. In this example, the output of ps is given as input to the grep command to search for desired process names under Unix and Linux. For multiple processes, use the egrep command as follows:

ps aux | egrep ‘app1|app2’ps aux | egrep ‘nginx|mysql|apache’ps aux | grep -E ‘nginx|mysql|apache’

Finding the process ID of a running program using the pidof

The pidof command finds the process id’s (pids) of the named programs. It prints those id’s (PIDs) on your screen. This program is on some systems used in run level change scripts, especially when the system has a System-V like rc structure. In that case these scripts are located in /etc/rc?.d, where ? is the runlevel. If the system has a start-stop-daemon program that should be used instead. For instance, here is how to see if mysqld or nginx running or not by finding its PID:

$ pidof nginx$ pidof mysqld

Final Words

If you need to manage or communicate with a process that is currently executing on your system, knowing the PID and PPID of the process can be useful. The PID (Process ID) and PPID (Parent Process ID) of a given process can be obtained in a variety of methods in Linux apps. A process, which is just a running instance of a software, is what controls how everything on your system operates. We hope our article on “How to Find PID of a Linux Process With pidof or pgrep” will surely help you to do so.