Virtualenv for Python: Yuck

vpy

#!/bin/bash -e
#
# Stay off my lawn
#
# I refuse to source scripts, so this is my way of dealing with virtualenv.
# 
# Basically the idea here is that I mess up my own personal environment so that
# this script runs in place of python.  With that I load the proper environment
# based on the python script being run.  Environment mapping is based on the
# canonical file path of each script.
#
# SETUP:
#	cp $0 ~/bin/vpy
#	(cd ~/bin; for k in {vpy,python}{2,2.7,3,3.7}; do
#		ln -s vpy "$k"
#	done)
# 
# USE:
#	vpy new myapp # or e.g. vpy2.7 if you want python2.7 specifically
#	vpy add myapp myapp.py
#	vpy pip myapp install mydep # or: vpy run myapp pip install mydep
#       ./myapp.py
#
# ALTERNATIVES:
#	- vex (https://github.com/sashahart/vex)
#       - virtualenvwrapper (http://virtualenvwrapper.readthedocs.org/en/latest/)
#	- capn (https://github.com/dustinlacewell/capn)
#	- pew (https://github.com/berdario/pew)
#	- inve (https://gist.github.com/datagrok/2199506)

me="$(readlink -f "$0")"
bn="$(basename "$me")"
name="$(basename "$0")"
default_version="3"
venv_base="$HOME/.virtualenv"
venv_env="$venv_base/environments"
venv_cfg="$venv_base/config"
version="$(echo "$name" | tr -d "[a-zA-Z-]")"

[ -d "$venv_base" ] || mkdir -p "$venv_base"
[ -e "$venv_cfg" ] || touch "$venv_cfg"

usage() {
	echo "Usage: $bn <command> [OPTIONS]"
	echo ""
	echo " Commands:"
	echo "   - new <env>           create a new environment named <env>"
	echo "   - del <env>           delete existing environment named <env>"
	echo "   - add <env> <prog>    add program to environment named <env>"
	echo "   - find <prog>         locate environment where program runs (if any)"
	echo "   - pip <env> <cmd...>  run pip in existing environment named <env>"
	echo "   - run <env> <cmd...>  run command in existing environment named <env>"
	exit 1
}

# we keep track of a file's abs. path by hashing it; that way we don't
# need to deal with special characters when storing it
vpy_hash() {
	readlink -f "$1" | sha1sum | cut -f1 -d' '
}

vpy_lookup() {
	sed -n '/^'"$(vpy_hash "$1")"'/s/^[^\s]\+\s\+//p' "$venv_cfg"
}

vpy_delete() {
	sed -i '/^[0-9a-f]* '"$1"'$/d' "$venv_cfg"
}

vpy_add() {
	key="$1"
	env="$2"
	sed -i '/^'"$key"'\s/d' "$venv_cfg"
	echo "$key $env" >> "$venv_cfg"
}

_vpy() {
	[ -z "$version" ] && version="$default_version"
	#[[ "$version" =~ [0-9].[0-9] ]] && version="-$version"
	[ $# -lt 2 ] && usage
	[ -z "$2" ] && usage
	env="$2"

	if [ "$1" == "new" ]; then
		mkdir -p "$venv_env/$env"
		exec "virtualenv${version:0:1}" --always-copy "$venv_env/$env"
	elif [ "$1" == "del" ]; then
		vpy_delete "$2"
		exec rm -rf "$venv_env/$env"
	elif [ "$1" == "add" ]; then
		[ $# -lt 3 ] && usage
		vpy_add "$(vpy_hash "$3")" "$env"
	elif [ "$1" == "find" ]; then
		vpy_lookup "$2"
	elif [ "$1" == "hash" ]; then
		vpy_hash "$2"
	elif [ "$1" == "pip" ]; then
		shift; shift
		. "$venv_env/$env/bin/activate"
		exec pip "$@"
	elif [ "$1" == "run" ]; then
		shift; shift
		. "$venv_env/$env/bin/activate"
		exec "$@"
	else
		usage
	fi
}

# finds the first file argument on a typical python command-line
firstfile() {
	lastchar=0
	for arg in "$@"; do
		if [ "${arg:0:1}" == "-" ]; then
			lastchar="${arg:1:2}"
			continue
		fi
		case "$lastchar" in [cWmX]) discard=1 ;; *) discard=0 ;; esac
		lastchar=0
		[ $discard -eq 1 ] && continue
		echo "$arg"
		return
	done
}

if [[ "$name" =~ $bn[0-9.]* ]]; then
	_vpy "$@"
elif [[ "$name" =~ python[0-9.]* ]]; then
	file="$(firstfile "$@")"
	[ -z "$file" ] || env="$(vpy_lookup "$file")"
	[ -z "$env" ] || . "$venv_env/$env/bin/activate"
	for ver in $(which -a "python$version"); do
		[ "$(readlink -f "$ver")" != "$me" ] && exec "$ver" "$@"
	done
	echo "Unable to find suitable python version matching \"python$version\""
	exit 1
fi