gistfile1.sh

#!/bin/bash
# Utility script that manage binary versioned symlinks.
#
# Supposing in /usr/local/bin, there is two executables: ruby1.8 and ruby1.9
# and /usr/local/bin/ruby is a symlink to ruby1.8.
#
# Running the scripts would do the following:
#
#   $ choose ruby list
#   Available ruby versions:
#     1.8 [Current]
#     1.9
#
#   $ sudo choose ruby set 1.9
#   $ choose ruby list
#   Available ruby versions:
#     1.8
#     1.9 [Current]
#
# To install simply copy to a folder on your path.
#
# Author: Rodrigo Kochenburger <divoxx@gmail.com>

BIN_NAME="$1"
COMMAND="$2"
VERSION="$3"
BIN_PATH="/usr/local/bin/$BIN_NAME"

if [ -z $BIN_NAME ] || [ -z $COMMAND ] || ([ $COMMAND == "set" ] && [ -z $VERSION ]); then
  echo "Usage: ./choose.sh <bin_name> [ list | set <version> ]"
  exit 1
fi

function extract_versions {
  local version
  for file in "$@"; do 
    version=`echo $file | grep -E "$BIN_NAME[0-9](.[0-9])*" | grep -Eo "[0-9](.[0-9])*"`
    echo $version
  done
}

if [ -a $BIN_PATH ]; then
  CURR_VER=$(extract_versions `readlink $BIN_PATH`)
fi

function list_versions {
  echo "Available $BIN_NAME versions:"
  
  for version in $(extract_versions $BIN_PATH*); do
    echo -n "  $version"
    
    if [[ $CURR_VER == $version ]]; then
      echo -n " [Current]"
    fi
    
    echo ""
  done
}

function set_version {
  rm -rf $BIN_PATH
  ln -s "${BIN_PATH}${VERSION}" $BIN_PATH
}

case $COMMAND in
  list) list_versions;;
  set) set_version;;
esac