How to Determine the Version of Ubuntu in a .sh Bash Script: A Comprehensive Guide

Linux systems, such as Ubuntu, are widely used in server environments and provide a rich ecosystem for developers. However, to ensure the smooth execution of various scripts and applications, knowing the exact version of the operating system is critical. In this guide, we will explore how to determine the version of Ubuntu using a Bash script. Specifically, we will discuss two techniques: reading the /etc/os-release file and using the lsb_release command. Both methods will be explained in detail, providing you with the necessary tools to accurately detect your Ubuntu version in a .sh script.

Method 1: Reading the /etc/os-release File

The /etc/os-release file is a standard configuration file that is part of the systemd distribution. It contains key information about the operating system, including the name, version, and release information. By reading this file, we can easily determine the version of Ubuntu running on a system.

# Open the /etc/os-release file
$ cat /etc/os-release

When you run this command, the output will typically look like this:

$ cat /etc/os-release
NAMEUbuntu
VERSION18.04.5 LTS (Bionic Beaver)
IDubuntu
ID_LIKEdebian
PRETTY_NAMEUbuntu 18.04.5 LTS
VERSION_ID18.04
HOME_URL
SUPPORT_URL
BUG_REPORT_URL
PRIVACY_POLICY_URL
VERSION_CODENAMEbionic
UBUNTU_CODENAMEbionic

From the output, you can extract the version information using various scripting techniques. Here’s an example of how to extract the version:

# Extract the Ubuntu version
$ VERSION_ID$(cat /etc/os-release | grep "VERSION_ID" | cut -d'' -f2)
$ echo $VERSION_ID

This script uses grep to find the line containing VERSION_ID and then cut to extract the value after the equal sign. This will output:

$ 18.04

Method 2: Using the lsb_release Command

The lsb_release command is another method for retrieving system information. Specifically, it provides detailed release information, including the distribution name, release code name, and version identifier. Here’s how to use it:

# Display the release information
$ lsb_release -r
Release:    18.04
# Display the distribution code name
$ lsb_release -c
Codename:   bionic

The first command will display the release version, while the second command will show the distribution code name. You can combine these commands in a Bash script to achieve the same result as reading the /etc/os-release file.

Implementing These Methods in a Bash Script

Below is a complete Bash script that uses these two methods to retrieve and display the Ubuntu version:

#!/bin/bash
# Method 1: Read /etc/os-release
VERSION_ID$(cat /etc/os-release | grep "VERSION_ID" | cut -d'' -f2)
if [ -z $VERSION_ID ]; then
  VERSION_ID"Not Found"
fi
# Method 2: Use lsb_release
lsb_release_output$(lsb_release -r)
LSB_RELEASE_RELEASE$(echo $lsb_release_output | awk '{print $3}')
if [ -z $VERSION_ID ]; then
  echo "Ubuntu Version: $VERSION_ID"
elif [ -z $LSB_RELEASE_RELEASE ]; then
  echo "Ubuntu Version: $VERSION_ID"
else
  echo "Ubuntu Version: $VERSION_ID (lsb_release: $LSB_RELEASE_RELEASE)"
fi

This script checks for both methods to ensure that you get the correct version information. If one method fails, it will use the other. This is particularly useful in environments where both methods might not be available or reliable.

Conclusion

Knowing the version of your Ubuntu system is crucial for maintaining compatibility and security. By utilizing the /etc/os-release file and the lsb_release command in Bash scripts, you can effectively determine your Ubuntu version. This knowledge is invaluable for developers, sysadmins, and any user who needs to ensure their system meets specific requirements.