Linux find process by command

Master Linux Kill Process Using ps, pgrep, pkill and More

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Managing processes in Linux can appear daunting to a new system administrator (sysadmin) at first. But with a little explanation and demonstration, you’ll learn how to find and perform Linux kill processes is just a matter of using command-line tools such as ps and kill .

In this article, you will learn commands for locating running and errant processes, killing (terminating) running processes, finding background processes, and much more on any Linux operating system.

By the end of the article, you will be managing processes based on process identification numbers (PIDs) from the command line like a Linux pro. Keep reading to learn all about process management commands in Linux!

Prerequisites

This article is going to be a walk-through of how to manage processes in Linux. If you want to be hands-on, you will need the following:

• A Linux host, which can be a virtual machine or a physical machine.
• To try the PowerShell examples, install PowerShell 7.1.1 on a Linux host.
• A non-root user account. While root access is not required, there will be an example where the root user can kill the running process of another user.

The distribution of Linux, you choose to use, is up to you. This article will be based on Ubuntu 20.04 LTS. However, the commands are standard for the Linux operating system.

Ready to get started? Good, let’s dive in.

Managing Processes in Linux

On occasion, you may run into a scenario where you need to stop a running process on a Linux system. As an example, you may have a bash script that runs on a schedule. That bash script is configured to run as another user via a cron job (Linux process scheduler).

Sometimes, this script spawns errant processes that can make the script fail. How do you kill those errant processes without rebooting the system or stopping the script?

In the next sections, you will walk through commands used to locate and terminate or kill processes on a Linux system. Each section will build on the last. You will learn about ps , top , pgrep , kill , and pkill commands all native to Linux.

As a bonus, PowerShell equivalent commands Get-Process and Stop-Process are included if Linux native commands are not your style.

Tools for Locating Processes

Before killing a process you must locate the correct process to target. The unique PID allows for precise targeting. Read on to learn how to locate the correct processes for termination.

Using the ps Command to Display Process Information

The Process Status or ps command displays information related to active processes on a Linux system. You can locate a running process and even background processes with ps .

The command ps will, by default, display all of the processes for the effective user identification (EUID) of the current user. Running the ps command, as shown below, will return every running process that your user can terminate.

Finding Expanded Process Information Using the top Command

What if you want to find constantly refreshing information on running processes and system metrics, in that case, you can use the top command. Unlike ps , the top command updates the process information on the screen over a set interval.

When you run the top command, you will see more than just a PID. Included with process details are CPU and memory percentages, Nice values (CPU scheduling process priority), and the process priority (PR) set by the Linux kernel.

For a new or experienced sysadmin, the top command is often the primary tool for managing vital system resources and processes. As shown below, the top command output displays more process information than the ps command including overall system metrics.

htop is an enhanced variant of top which includes various improvements, such as a colorized terminal output.

Let’s say you’d like to inspect the memory or CPU resources a process is consuming. In that case, you can use the p switch of top as shown below.

Perhaps you need to display all running processes for a specific username. The top command offers the u switch to display only a specific user’s processes. As seen in the example below, PIDs matching only the user ID bkindle are shown.

Locating Specific Process PIDs with the pgrep Command

Originally a Solaris command, pgrep was ported for use with Linux. Combining the search power of the grep command and the process management of ps , pgrep offers flexibility in finding the exact process to target.

Although ps displays more information, pgrep is designed to return only the PID of the returned processes. pgrep helps with locating the process using the many available search parameters. In the following example, pgrep is shown searching for any process matching vmtoolsd .

Similarly, specify a user ID with the u switch to retrieve only processes associated with that specific user. As shown below, only a single PID is returned for the user bkindle and the vmtoolsd process.

Finding Processes with PowerShell’s Get-Process in Linux

Typical Linux commands work great, but did you know PowerShell is able to manage Linux processes too? The Get-Process cmdlet works similar to the Linux ps command and returns process information. For example, perhaps you need to find all running processes by the current user, bkindle . As shown below, find all PIDs (labeled ID by Get-Process ) of the user bkindle .

Get-Process -IncludeUserName | Where-Object | Select-Object -Property 'Id','UserName','ProcessName' 

Having learned how to locate different processes, read on to discover all the ways to terminate or kill a process in Linux!

Killing Processes Using the Kill Commands in Linux

In previous sections, you learned how to locate the PID of the process you want to send a kill signal to using native Linux and PowerShell commands. The next sections will explain how to use the kill and pkill programs, its associated signals, and command-line switches.

Linux Signals and Process Management

Signals are the method that Linux uses to communicate with processes running in the operating system. The three primary signals that the kill command uses to terminate processes are:

• 1 (SIGHUP) – Terminates interactive programs and causes daemons (background services) to re-read the configuration files the process uses.
• 9 (SIGKILL) – Forces the process to exit without performing graceful shutdown tasks.
• 15 (SIGTERM) – Allows a process to terminate gracefully, such as closing open files when finished. This is the default signal used when no number is specified when using the kill command.

While this article only focuses on the three main signals used for killing processes, there are a total of 64 available signals. Use kill -l to get the list of signals and their corresponding number.

The killall command will terminate all processes based on a name instead of PID, which can make this command pretty destructive if used carelessly. If you choose to use this command, however, use the i option to cause the command to ask for confirmation.

Killing Processes by Name with pkill

You may have noticed that the kill command only works with process IDs. This can make terminating a process a complicated multi-step process. The pkill command, included in the procps and procps-ng packages, terminates a process based on a searched name.

Functionally, the pkill command acts as a wrapper around the pgrep program. The pkill command sends a specified signal to each process found instead of only listing the PIDs in the terminal. pkill differs from kill in that pkill can only use the name of a process, not the PID.

The pkill command is not available, by default, in Ubuntu 20.04 LTS. You will have to download and install the application. To do so, run sudo apt install mcollective-plugins-process -y .

To kill a process using pkill , perform the following steps:

1. Use ps to verify the nano application (a command-line text editor) is currently running. This step is optional, but a safety check before killing a process.
2. Use pkill -9 nano to forcefully terminate the nano application.

Shown below is an example of the above process from an Ubuntu 20.04 LTS bash terminal.

Killing a Process with the Top Command

When you run the top command to view running processes, you can kill a given process with the k keystroke. You’ll see an interactive prompt asking for the PID of a process to kill.

As shown below, run the top command and press k. Enter the PID that you want to kill, and press the Enter key to immediately terminate the PID.

Next, learn one more alternative to native Linux commands using the PowerShell Stop-Process command!

Using the PowerShell Stop-Process Command to Terminate a Process

If Linux native commands aren’t your style, PowerShell has you covered! Just as with the kill command, you can terminate processes using the Stop-Process cmdlet in Linux. Once again, pretend you are running a PowerShell pwsh process.

1. Find the PID with Get-Process -ProcessName ‘pwsh’ and note the PIDs to terminate.
2. Use Stop-Process -Id 29992,30014 to terminate the multiple processes returned.
3. Use Get-Process -ProcessName ‘pwsh’ and verify the PIDs, 29992 and 30014 are no longer listed, meaning they have been terminated.

You can also use Get-Process and the kill method to terminate one or multiple processes: (Get-Process -Id [PID]).Kill() or (Get-Process -Id [PID1,2,3,4]).Kill() .

Exercise caution when using the ProcessName parameter. Using this parameter behaves similar to the killall command, and will kill all processes matching the name(s) provided.

Below is an example of the above process from an Ubuntu 20.04 LTS bash terminal.

Next Steps

You should now know the many ways to find and terminate processes in Linux! For your next challenge, try killing processes remotely using SSH connections or by killing processes that may be running in containers.

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How do I search for a process by name without using grep?

OP just wants a shorter command I’d guess. If there would be a thing like ps -n that would answer his need. ps -n firefox is a bit shorter than ps | grep firefox . ps can already filter on pid or processes for a user id, so it’s a reasonable question to filter on process name.

8 Answers 8

The pgrep command, and its sibling pkill , exists precisely for this purpose:

• pgrep firefox will list all processes whose commands match firefox
• pgrep -f firefox will list all processes whose entire command lines match firefox
• pgrep -x firefox will list all processes whose commands exactly match firefox
• . and so on.

And naturally, pgrep will exclude itself from the match, so none of the grep rituals associated with ps | grep are needed.

The other set of tools for this are the pidof and killall commands. These aren’t as flexible as pgrep and pkill .

Useful if you have a long command name and/or command line args is pgrep -f foo which uses the full process name to match foo

 -C cmdlist Select by command name. This selects the processes whose executable name is given in cmdlist. -f Do full-format listing. This option can be combined with many other UNIX-style options to add additional columns. It also causes the command arguments to be printed. When used with -L, the NLWP (number of threads) and LWP (thread ID) columns will be added. See the c option, the format keyword args, and the format keyword comm. 

This is the best answer but unfortunately doesn’t work on OSX. The BSD ps -C flag behaves completely differently — «Change the way the CPU percentage is calculated»

You will get all the processes with names

exmple: 1747 568 568 ? 00:00:00 colord 1833 1832 1832 ? 00:00:00 gnome-keyring-d 2263 568 568 ? 00:00:00 udisksd 2311 2311 2311 ? 00:00:00 cupsd 2315 2315 2311 ? 00:00:00 dbus 

Redirect or so copy the output to a file and then open nano , press Ctrl + W and you can search for the name you want.

top allows you to search for string when you hit uppercase L ; the process will be highlighted, and use up and down arrow keys to scroll through list of processes. Similarly, htop command allows highlighting a particular process when you hit / . And \ will filter all the processes with a particular string in the name.

For those who like awk, here’s an awk oneliner: ps -eF | awk ‘/process-name/ ‘ . With ps -eF process name is always in 11th column. Alternatively if you do ps -eF | awk » | sort you get a sorted list of processes names, sorted alphabetically. Pipe it into less command just to view the long list of files easier.

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