Ting-Wei Lan authored Dec 01, 2018 and Georges Basile Stavracas Neto committed Dec 01, 2018

This commit includes following fixes for a few shell scripts:

1. Follow the best practice of quoting variables everywhere unless they
   are used in places where word-splitting and globbing can never happen.

2. Replace `command` with $(command) because the latter is easier to use
   and read.

3. Don't use "$@" in places expecting a string because it is an array
   of strings instead of a single string.