Pip install and save to requirements.txt

pips.sh

# Pip install and add to requirements.txt and sort requirements.txt
# Flags: -d  Use -d at the beginning! to add dev-requirements.txt instead 
# TODO: Use extras from pip show, see https://github.com/pypa/pip/issues/4824
# Uses perl with \Q to perform a literal substitution

function pips ()
{
  local REQS_PATH='requirements.txt'
  local OPTIND=1 # Reset index

  while getopts ":d" opt; do
      case $opt in
          d)
              local REQS_PATH='dev-requirements.txt'
          ;;
          \?)
              echo "Invalid option: -$OPTARG" >&2
              exit 1
          ;;
      esac
  done

  shift "$((OPTIND-1))"

  for p in "$@"
  do
      pip install $p
      local EXTRAS=$(echo $p | grep -o "\[\w*\]")
      pip show $(echo $p | perl -pe "s|\Q$EXTRAS||") | awk 'NR==1,NR==2 {print $2}' | sed -z "s/\n/$EXTRAS==/" >> $REQS_PATH
  done

  sort -u $REQS_PATH -o $REQS_PATH
}