How to get process ID of background process?

🤔 How to get process ID of background process?

We all know the frustration of starting a background process in our shell script and not being able to track or control it effectively.

So, how do we get the process ID (PID) of a background process from our shell script? 🤷‍♂️

The Issue

Let's take a look at the context: you start a background process in your shell script, and you want to be able to kill this process when your script finishes.

The problem arises when trying to retrieve the PID of the background process. You might think that the variable $! would give you the PID of the background process, but unfortunately, that's not the case. 😫

The Solution

But fear not! There are actually a couple of simple solutions to this problem. Let's dive in and check them out:

1. Using pgrep

One way to get the PID of a background process is by using the pgrep command. This command allows you to search for a process using various criteria, including the process name.

Here's an example of how you can use pgrep to retrieve the PID of your background process:

#!/bin/bash

# Start your background process
your_background_process &

# Get the PID of the background process
pid=$(pgrep -f "your_background_process")

echo "PID: $pid"

In the example above, pgrep -f "your_background_process" searches for a process whose name matches "your_background_process" and returns its PID. Make sure to replace "your_background_process" with the actual name of your background process.

2. Using a Temporary File

Another approach is to write the PID of the background process to a temporary file. This method allows you to easily access the PID at any point in your script.

Here's how you can implement this solution:

#!/bin/bash

# Start your background process
your_background_process &

# Write the PID of the background process to a temporary file
echo $! > bg_process.pid

# Retrieve the PID from the temporary file
pid=$(cat bg_process.pid)

echo "PID: $pid"

In this example, we create a temporary file called bg_process.pid and write the PID of our background process to it ($!). Later on, we can retrieve the PID from the file using cat bg_process.pid.

Call-to-Action

Now that you have two easy methods to get the PID of your background process, go ahead and try them out! 💪

If you found this guide helpful, make sure to share it with your friends and colleagues who might be facing the same issue. And if you have any other tips or tricks, feel free to leave a comment below and keep the conversation going! 🙌