npm install's all required packages in a file, using sed and xargs, --save-dev and --save optional

install-required-packages.sh

#!/bin/bash
#
# npm install all required packages 
# example usage
#
# ./install-required-packages.sh gulpfile.sh --save-dev
# ./install-required-packages.sh gulpfile.sh --save
# ./install-required-packages.sh gulpfile.sh
#
# TODO: this matches require's that are commented out. Fix.
# TODO: doesn't match multiple requires on one line. But do you really want to ever write code like that?

FILENAME=$1
shift
sed -e "/\(.*\)require('\([-A-Za-z0-9]*\)')\(.*\)/!d" \
    -e "s/\(.*\)require('\([-A-Za-z0-9]*\)')\(.*\)/\2/" $FILENAME \
    | xargs -L1 npm install "$@"