Simple application version manager

v-switch

#!/bin/bash

# Application name
APP_NAME="PHP"

# Active application directory
# The directory with all the versions of the application must be this directory prefixed with the version
PHP_ROOT="/c/${APP_NAME}"

# The file that keeps the current application version
CURRENT_FILE="${HOME}/.${APP_NAME}-current"

# Check if there's a currently selected version
CURRENT_VERSION=
if [ -f "${CURRENT_FILE}" ]; then
    CURRENT_VERSION="$(cat ${CURRENT_FILE})"
fi

# Check if the requested version is already active
if [ "${CURRENT_VERSION}" -eq "${1}" ]; then
    echo "${APP_NAME} version ${1} is already selected."
    exit 0 # Nothing to do, but the request version is selected
fi

# Check if the folder with the requested version exists
if [ ! -d "${PHP_ROOT}${1}" ]; then
    echo "The ${APP_NAME} version ${1} could not be found."
    exit 1 
fi

# Check if the directory of the selected version exists
if [ -d "${PHP_ROOT}" ]; then
    # Check if the current version could be retrieved from the $CURRENT_FILE
    if [ ! "${CURRENT_VERSION}" ]; then
        # If the directory exists and the version file don't, there's a problem the script can't solve
        echo "There's a currently selected version of ${APP_NAME}, but the version file (${CURRENT_FILE}) could not be found.";
        echo "This requires manual intervention, either create the file ${CURRENT_FILE} with the current version as content or move the ${PHP_ROOT} folder."
        exit 1
    fi

    # Move the currently selected version to a version directory name
    mv "${PHP_ROOT}" "${PHP_ROOT}${CURRENT_VERSION}"
fi

# Move the requested version to the selected version
mv "${PHP_ROOT}${1}" "${PHP_ROOT}"

# Stores the currently selected version in the file
echo "${1}" > "${CURRENT_FILE}"

echo "${APP_NAME} version ${1} selected."