pathctl

README.md

pathctl

A quick and dirty script for loading/appending to PATH

Oftentimes when I write install scripts i have to go looking for a path and its presence to avoid duplication, parsing the .bashrc and .profile scripts .

This is tedious, and prone to issues.

If we could have a basic utility that already took care of this as a default item in the system, it would be handy.

This gist contains one such implementation, in Python 3.

I intend to re-write this in Rust as an excercise, for learning.

The following are the requirements I set out for myself, for reference. If anyone would like to have a go and "standardize" on the excercise, do feel free. It would be neat to get it into a major distro, but I'm not holding my breath.

• ~/.PATH file contains user's paths, one per line. Lines may be empty. Lines starting with '#' are comments and are to be skipped
• command may take the argument load to print a path-notation of paths, each separated by colon
• command may take the arguments add DIR_PATH which will add the path to the end of ~/.PATH
• command may take the argument version which will print the version string alone
• any other argument form causes help to be printed, and exits with error code
• any error should cause print out of error message, without printing stack traces or other debugging noise

In my case, I also check for duplication, though this is not a requirement. I also print the new path notation after adding, again this is not a requirement.

pathctl

#!/usr/bin/env python3

# LICENSE: "MIT Expat License" (SPDX: MIT-0)
# Do as you wish with this code.
# No warranty or guarantees on suitability, etc.

r"""
Managed paths script


Create an easy target for adding new PATH entries


Install utility:

    [[ -f ~/.PATH]] || touch ~/.PATH
    # (add custom paths as required to .PATH file)

    sudo cp pathctl /usr/local/bin/pathctl


Use in .bashrc:

    export PATH="$PATH:$(pathctl load)"


Use in installation scripts:

    if [[ -f ~/.PATH ]]; then
        pathctl add .../new/path
    else
        echo "Add '.../new/path' to your \$PATH. Consider using 'pathctl'"
    fi


"""

import os
import sys

VERSION="0.0.1"
PATHFILE_PATH = os.path.expanduser("~/.PATH")


def warn(message):
    print(f"warn: {message}", file=sys.stderr)


def line_check(line):
    if ':' in line:
        warn(f"Invalid path: {line}")
        return False

    if line.strip().startswith("#"):
        return False

    return True


def load_lines(filepath):
    with open(filepath) as fh:
        resolved_lines = [L.strip() for L in fh.readlines() if line_check(L)]
    return resolved_lines


def append_path(filepath, target):
    target = target.strip()

    try:
        paths = load_lines(PATHFILE_PATH)
    except FileNotFoundError:
        paths = []

    if target in paths:
        warn(f"Path already present: {target}")
        display_paths(paths)

    else:
        with open(filepath, 'a') as fh:
            fh.write(f"{target}\n")
        display_paths([*paths, target])


def display_paths(paths):
    print(':'.join(paths))


def main():

    if sys.argv[1:] == ['version']:
        print(VERSION)
        return

    elif sys.argv[1:] == ['load']:
        display_paths(load_lines(PATHFILE_PATH))

    elif len(sys.argv) == 3 and sys.argv[1:2] == ['add']:
        append_path(PATHFILE_PATH, sys.argv[2])

    else:
        raise Exception(f"""Load "~/.PATH" as a `$PATH` string, or append a new path to it

        {sys.argv[0]} load
        {sys.argv[0]} add DIRECTORY
        """)


if __name__ == "__main__":
    try:
        main()
    except Exception as e:
        print(e)
        exit(1)