Dependency checker and installer for node.js and npm

install_node_and_npm.sh

#!/bin/bash -e
#
# This script checks if useful versions of node.js and npm are installed
# on the system, and if not it attempts to install them.
#
# Should work on Debian based systems and OS X.
# So far tested on Kubuntu 12.04.
#

_die(){
    echo "ERROR: $*"
    echo
    echo "You need to manually install the dependencies in order to contine."
    exit 1
}

_is_git_installed(){
    _v="$( git --version )"
    if [[ "$_v" =~ \ 1\.[7-9] ]]  ||  [[ "$_v" =~ \ 2\. ]] ; then
        return 0
    else
        return 1
    fi
}

_is_node_installed(){
    _v="$( node -v )"
    if [[ "$_v" =~ v0\.8 ]]  ||  [[ "$_v" =~ v1 ]] ; then
        return 0
    else
        return 1
    fi
}

_is_npm_installed(){
    _v="$( npm -v )"
    if [[ "$_v" =~ ^2 ]] ; then
        return 0
    else
        return 1
    fi
}

_install_node(){
    case $OSTYPE in
        linux*)     _install_node_on_linux_with_apt_get
            ;;
        darwin*)    _install_node_on_osx_with_brew
            ;;
        *)          _die "Unknown OS"
            ;;
    esac
}

_install_node_on_osx_with_brew(){
    if ! which brew ; then
        _die "I need brew, I think. Feel free to improve the install script."
    fi

    # See https://gist.github.com/579814
    PREFIX="$( brew --prefix )"
    sudo mkdir -p $PREFIX/{share/man,bin,lib/node,include/node}
    sudo chown -R $USER $PREFIX/{share/man,bin,lib/node,include/node}
    brew install node
    node -v
}

# See http://ariejan.net/2011/10/24/installing-node-js-and-npm-on-ubuntu-debian
_install_node_on_linux_with_apt_get(){
    if ! which apt-get >/dev/null ; then
        _die "apt-get not found. Feel free to improve the install script."
    fi
    if [ -d ./node ] ; then
        _die "Will not overwrite existing folder: `pwd`/node"
    fi

    sudo apt-get update
    sudo apt-get install git-core curl build-essential openssl libssl-dev
    _owns_node_folder=yes
    git clone https://github.com/joyent/node.git
    cd node
    git checkout v0.8.8
    ./configure
    make
    sudo make install
    cd -
    node -v
}

_install_npm(){
    if [ -d ./node ] ; then
        _die "Will not overwrite existing folder: `pwd`/npm"
    fi
    _owns_npm_folder=yes
    git clone http://github.com/isaacs/npm.git
    cd npm
    # assume that master is stable
    ./configure
    make
    sudo make install
    cd -
    npm -v
}

_main(){
    if ! _is_git_installed ; then
        # Should 'never' happen actually (unless a wizard is at the keyboard).
        _die "Seems like you checked out a git repo without having git...(?)"
    fi
    if ! _is_node_installed  ; then
        echo "Installing node.js ..."
        _install_node  || _die "It seems like installation of node.js failed"
    else
        echo "node OK"
    fi
    if ! _is_npm_installed ; then
        echo "Installing npm ..."
        _install_npm || _die "It seems like installation of npm failed"
    else
        echo "npm OK"
    fi
}

_cleanup(){
    if [ -d ./node ] && [ $_owns_node_folder ] ; then
        rm -rf ./node
    fi
    if [ -d ./npm ] && [ $_owns_npm_folder] ; then
        rm -rf ./npm
    fi
}


# MAIN:

# Cleanup on exit and allow smooth ^C.
trap exit INT
trap _cleanup EXIT

_main