Environment Modifier

This utility acts similar to the coreutils env application (/usr/bin/env), but with one added feature: when running an application or script that resides in a known directory, it can replace the application with a known alternative.

For example, say you have the following directory structure:

project/
  code/
    script.py  <-- Python script starting with: #!/usr/bin/env python3
  venv/        <-- Python virtual environment

By default, if you run ./project/code/script.py on the command line, it will execute with the system Python installation found by /usr/bin/env python3 (typically /usr/bin/python3).

Instead, we can define a file project/.envmod with the following:

python3=venv/bin/python3

Now, when we run script.py, it will use the virtual environment instead.

Installation

1. Clone this repository.
2. Install the wrapper in place of /usr/bin/env:

   sudo ./envmod --install
   

3. Create a .envmod file as described below.

.envmod File

The .envmod file is used to specify alternative applications to be executed. Each line in the file contains a pattern structured as follows:

application=path/to/alternative

where application is the name of the program specified to /usr/bin/env that should be replaced. path/to/alternative should be either an absolute path, or a path relative to the parent directory where .envmod is located.

By default, config files are loaded in the following order of precedence:

1. .envmod located in the same directory as the script being run (see below), or in any parent directory, with patterns from higher level directories being overridden by those in lower level directories.
2. ${HOME}/.envmod
3. /etc/envmod