How to detect OS system using BASH?

Question

The script should be able to detect the operating system that is running. The alternatives OS is Arch Linux, Centos and Ubuntu.

os=$(uname) 
if [ "$os" == "Arch" ]; then   
  echo "Arch Linux detected" 
elif [ "$os" == "CentOS" ]; then   
  echo "CentOS detected" 
elif [ "$os" == "Ubuntu" ]; then   
  echo "Ubuntu detected" 
else   
  echo "Unknown OS detected"
fi```

Output: Unknown OS detected


I tried doing this:

\`del1()

{
os=$(cat /etc/os-release | grep "PRETTY_NAME")
}
del1

echo "The operating system is: $os"\`

The output: PRETTY_NAME="Ubuntu 20.04.2 LTS"

But I want to check between Centos, Arch Linux and Ubuntu.

Any suggestions?

Answer 1

The uname command will always return Linux when running on Linux, so of course that's never going to work.

Using /etc/os-release is probably the best solution, but don't grep it for information; the file is a collection of shell variables that you can source with the . command, so you can write something like this:

#!/bin/sh

. /etc/os-release

case $ID in
  ubuntu) echo "This is Ubuntu!"
    ;;

  arch) echo "This is Arch Linux!"
    ;;

  centos) echo "This is CentOS!"
    ;;

  *) echo "This is an unknown distribution."
      ;;
esac