bash shell store path to current file as variable?

Question

When starting a project in Python, I want to save some environment variables in a file called environment_variables and source this file in the bashrc.

The file looks something like this:

username=$(whoami)

# project root path
export PROJECT_DIR='/home/'$username'/nuclei_segmentation/'

# project data path
export DATA_DIR=$PROJECT_DIR"data/"

# location of models 
export MODEL_DIR=$PROJECT_DIR"models/"

# project output data
export OUTPUT_DIR=$PROJECT_DIR"output/"

I would like to change the PROJECT_DIR path so it is platform/name independent. So this environment_variables file will always be in the root directory of the project and I want to set PROJECT_DIR to always be the location of the environment_variables file.

I thought I could do this with PWD but when called from bashrc this creates an error, I also thought of a solution using find to search for the file from the root directory but this seems to complex and think there must be a better way?

Answer 1

If I am understanding at all where you want to go with this, my recommendation would be

• Make the code work out of the current directory as far as possible.
• Don't litter the user's environment with multiple variables if it can be avoided.
• If you have to have environment variables, give them a name which clearly communicates what they are related to.

In some more concretion, a single variable which names the project root should be all you really need. Don't require it to be set if the expected files are in the current directory.

export NUC_SEG_DIR=$HOME/nuclei_segmentation

In your Python code, put in reasonable defaults. In this particular case, expect os.path.join(os.environ['NUC_SEG_DIR'], 'data') to point to your data directory, etc. If users want to override this, that's easy enough with symbolic links. Make sure this is parametrized in the code so that it's easy to override in a single place if you should want to make this configurable in the future. Maybe something like

def nuc_seg(root_dir=os.environ['NUC_SEG_DIR'], data_dir='./data', model_dir='./models', output_dir='./output'):
    if root_dir == '':
        root_dir='.'
    ... your code here

and perhaps later on make your command-line interface let the user override these values by way of command-line options or a configuration file.

Again, don't require the user to edit their .bash_profile or similar - what if they want to run multiple experiments in different directories, or whatever? They can figure out how to make the environment variable permanent, or you could even document this as an option if your users can't be expected to be familiar with the basics of the shell.

Answer 2

Use dirname $0 inside script file to find the directory where current script file resides