CADESUser DocumentationLinuxEnvironment Customization

Environment Variables

Before Starting

Consider these important facts:

  • Environment variables are all upper case.
  • To use their values, precede the name with a $.

Initializing Your Environment

Linux utilizes Bash as the default shell and when a session started it reads commands from ~/.bash_profile.

Environment variables are set in the file ~/.bashrc.

📝 Note: The files ~/.bash_profile and .bashrc are hidden. To list hidden files, type ls -a.

Know the Environment Variables

Here is a list of some common environment variables:

  • $HOME - Path of your home directory
  • $PATH - List of directories where the system checks for programs to run
  • $LD_LIBRARY_PATH - List of directories where the system checks for shared libraries to load
  • $HOSTNAME - The name of the host, e.g. or-condos-login.

📝 Note: See the values of all your environment variables by typing env on your terminal.

Working with the Environment Variables

  • Display the value of an environment variable using echo:

    echo $HOME
    /home/UID
    
  • Modify the value of environment variables with export:

    export PATH=$PATH:/home/UID
    export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/UID/custom_lib_directory
    
  • Set a value for environment variables:

    export OMP_NUM_THREADS=12
    

    This command sets the value of the variable called OMP_NUM_THREADS (an OpenMP parameter) to 12.

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