Linux pidof Command with Practical Examples

Introduction

In this lab, you will learn how to use the pidof command in Linux to find the process ID (PID) of a running process. The pidof command is a useful tool for system monitoring and management, as it allows you to quickly identify the PID of a process, which can be helpful when you need to interact with or terminate a specific process. You will start by understanding the basics of the pidof command, and then practice finding the PID of a running process and locating multiple processes with the same name.

Linux Commands Cheat Sheet

Understand the pidof Command

In this step, you will learn about the pidof command in Linux, which is used to find the process ID (PID) of a running process.

The pidof command is a useful tool for system monitoring and management. It allows you to quickly identify the PID of a process, which can be helpful when you need to interact with or terminate a specific process.

To use the pidof command, simply provide the name of the process you want to find the PID for. For example, to find the PID of the nginx process, you can run:

pidof nginx

Example output:

1234 5678

The output shows that there are two processes running with the name nginx, and their PIDs are 1234 and 5678.

The pidof command can also be used to find the PID of a process that was started by a specific command. For example, to find the PID of the python3 process that is running a script named my_script.py, you can run:

pidof -x my_script.py

Example output:

9012

The -x option tells pidof to look for the PID of the process that was started by the specified command, rather than just the process name.

In the next step, you will learn how to use the pidof command to find the PID of a running process.

Find the PID of a Running Process

In this step, you will learn how to use the pidof command to find the process ID (PID) of a running process.

First, let's start a new process that we can use for this example. Open a new terminal and run the following command to start a simple Python script:

python3 -c "import time; print('Running process...'); time.sleep(60)"

This will start a Python process that will run for 60 seconds, printing "Running process..." to the console.

Now, in a separate terminal, you can use the pidof command to find the PID of the running Python process:

pidof python3

Example output:

12345

The output shows the PID of the running Python process, which in this case is 12345.

You can also use the ps command to verify the PID and the process information:

ps -p 12345 -o pid,comm

Example output:

  PID COMMAND
12345 python3

The ps command confirms that the PID 12345 belongs to the python3 process.

Now that you know how to find the PID of a running process, you can use this information to interact with or terminate the process as needed.

Locate Multiple Processes with the Same Name

In this step, you will learn how to use the pidof command to locate multiple processes with the same name.

Let's start by running two instances of the nginx web server:

sudo nginx
sudo nginx

Now, you can use the pidof command to find the PIDs of the running nginx processes:

pidof nginx

Example output:

1234 5678

The output shows that there are two nginx processes running, with PIDs 1234 and 5678.

You can also use the ps command to view more details about the running nginx processes:

ps -p 1234 -o pid,comm
ps -p 5678 -o pid,comm

Example output:

  PID COMMAND
 1234 nginx
 5678 nginx

The ps command confirms that both PIDs belong to the nginx process.

If you want to target a specific nginx process, you can use the PID to interact with it. For example, to stop a specific nginx process, you can run:

sudo kill 1234

This will terminate the nginx process with PID 1234.

In summary, the pidof command is a useful tool for locating multiple processes with the same name, and the PIDs can be used to target and manage those processes individually.

Summary

In this lab, you learned about the pidof command in Linux, which is used to find the process ID (PID) of a running process. You understood that the pidof command is a useful tool for system monitoring and management, allowing you to quickly identify the PID of a process, which can be helpful when you need to interact with or terminate a specific process. You also learned how to use the pidof command to find the PID of a running process, including the ability to find the PID of a process that was started by a specific command.

Linux Commands Cheat Sheet