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A simple, file-system-based install utility

Background

An installation makes certain files available under certain directories.

For instance:

  1. Making executable files available under a directory listed in your PATH environment variable.
  2. Making system libraries available under a directory listed in your LIBRARY_PATH environment variable.
  3. Making Python libraries available under a directory listed in your PYTHON_PATH environment variable.
  4. Making Git hooks available under a .git/hooks directory (or .git\hooks on Windows).
  5. Making configuration files (e.g., .vimrc) available under your home directory.

install.py aims to provide simple, robust, and reusable means to these ends, and beyond.

Analysis

Design Goals

In the following, the keyword "SHOULD" is to be interpreted as described in RFC 2119.

  1. install.py SHOULD be easy to use in, or adapt to a small project.
  2. install.py SHOULD be cross-platform.
  3. install.py SHOULD make it easy to keep installed files up-to-date.

Symbolic Links

Most file-systems allow for files to be copied from one directory to another. Copying has the down-side that a copy may become out of date with the source. Some file-systems tackle this by allowing "symbolic links": files that seamlessly refer to other files.

Symbolic links are generally available in contemporary file-systems for Unix-like operating systems and on Windows since Windows 6.0 (Vista).

Related Tools

Implementation

The utility is implemented as a standalone Python file, install.py.

User Guide

Where is the Python script?

To ensure proper accreditation, manage releases, and reduce code duplication, install.py is generated from an m4 template. To get the shell script, either:

  1. Fetch the latest release of the shell script, or;

  2. Type make to build it, if you happen to have the m4 macro processor installed.

    Please note, the last step of building install.py is to execute git-ready-to-deploy.sh. This ensures a clean release of install.py, so long as you mind the exit code of make.

What do I do with the Python script?

Copy install_py into the directory containing the files that you would like to install. Create an INI file, (e.g., called config.ini) having a install.py section with the properties src_dir, dst_dir, and files. The values of the properties may be arbitrary Python expressions, evaluating to the types str, str, and List[str], respectively. This is to allow you to specify the configuration in a platform-independent way.

For instance, you might have a hooks directory in your Git repository, having an install.py, and a config.ini that looks like this:

[install.py]
src_dir = os.path.dirname(__file__)
dst_dir = os.path.join(src_dir, '..', '.git', 'hooks')
files = ['pre-commit', 'pre-push']

This will take the location of the executing install.py as src_dir, its sibling directory ../.git/hooks/ (or ..\.git\hooks on Windows) as dst_dir, and look for the files pre-commit and pre-push to install from src_dir into dst_dir.