The code `. /etc/os-release` is a shell command that sources...

The code . /etc/os-release is a shell command that sources the file /etc/os-release. Here's what it does:

1. File Sourcing (.):
   The single dot (.) is a shorthand for the source command in many Unix-like shells (e.g., bash). Sourcing a file executes the commands in that file in the current shell environment, rather than in a new subshell.

2. File /etc/os-release:
   This is a standard file in most Linux distributions that contains environment variables describing the operating system. For example, it typically contains variables like:

   • NAME: The OS name (e.g., "Ubuntu").
   • VERSION: The OS version.
   • ID: A short identifier for the OS (e.g., "ubuntu").
   • PRETTY_NAME: A human-readable name for the OS.
   • Other metadata about the operating system.

3. Effect of This Command:
   By sourcing /etc/os-release, the script or shell session reads the variables in that file and makes them available as shell environment variables. For example:

   . /etc/os-release
   echo $NAME
   

   This would output the name of the operating system, such as "Ubuntu".

In summary: This command reads the variables defined in /etc/os-release and makes them available in the current shell session for use in subsequent commands or scripts.