Set environment variables in Linux

When you input a command, the system will search the executable file in the directories specified by the environment variable PATH. If there are multiple directories containing the target file (e.g., multiple versions of the same software), the file in the directory with the highest priority will be executed.

1. Check existed environment variables

    echo $PATH
   

   You can find that PATH is a list of paths separated by :.

2. Add environment variables temporarily

    export PATH=/dir/you/want/to/add:$PATH
   

3. Add environment variables permanently

   Add the command export PATH=/dir/you/want/to/add:$PATH to ~/.bashrc, then restart the shell or source ~/.bashrc.

4. Add/modify environment variables in conda (reference)

    # set env vars `my_var` as `value`
    conda env config vars set my_var=value
    # check env vars in this env
    conda env config vars list
    # unset env vars in this env
    conda env config vars unset my_var -n test-env
   

5. use conda env in bash

    # check the module name of miniconda/anaconda
    module load miniconda/3
    source activate <env-name>
    # or
    # conda activate <env-name>