Write and use a simple bash script to kill a process to free up a port.

This article was first published on my dev.to page, check it here - https://dev.to/guha/kill-that-pesky-process-the-really-lazy-way-5eg.

This is going to a be a quick one, today i’m going to share a small bash script that has saved me precious seconds or maybe even whole minutes over the years, every time i want to kill a process to free up a port.

Why

Something is already running at port 9000

I run into one of these every once in a while.

With me it often happens when i SUSPEND (CTRL+Z) my dev server instead of KILLING (CTRL+C) it.

The next steps would often involve hunting down the pid of the process running on that port and killing it.

Easy enough, but here’s something easier.

How

1. cd to /usr/local/bin/.
2. Create a new file and name it stop or anything else you want.
3. Paste the following into it

      #!/bin/bash
      touch temp.text
      lsof -n -i4TCP:$1 | awk '{print $2}' > temp.text
      pidToStop=`(sed '2q;d' temp.text)`
      > temp.text
      if [[ -n $pidToStop ]]
      then
      kill -9 $pidToStop
      echo "!! $1 is stopped !!"
      else
      echo "Sorry nothing running on above port"
      fi
      rm temp.text
   

   *disclaimer: i didn’t write the script, i merely adopted it. Credits below.

4. chmod +x stop to make the file executable. chmod 755 also works.
5. Now you can use stop 9000 or any other port anytime on the terminal to stop whatever process is running on that port.
6. Profit. Write once, use always.

Very briefly, what the script above does is find the pid of the process running on the input port, copy it to a temp file and then read the temp file to find the pid in it and kill it, finally deleting the temp file. awk for those curious is a programming language used for text processing.

Notes

• Here’s my gist with the script above.
• Here’s the stackoverflow answer i originally found this script at.