I had a casual read on the book “Bash Idioms” by Carl Albing. I scribbled what I learned from what stuck me the most. There are so much more. Please read the book instead.

Lesson 1: “A And B” are true only if both A and B are true…..

Example 1: If the cd command succeeds, then execute the “rm -Rv *.tmp” command

cd tmp && rm -Rv *.tmp

Lesson 2: If “A is true”, “B is not executed” and vice versa.

Example 2: Change Directory, if fail, put out the message that the change directory failed and exit

cd /tmp || { echo "cd to /tmp failed" ; exit ; }

Lesson 3: When do we use the [ ] versus [[ ]]?

I learned that the author advises BASH users to use the [[ ]] unless when avoidable. The Double Bracket helps to avoid confusing edge case behaviours that a single bracket may exhibit. If however, the main goal is portability across various platform to non-bash platforms, single quota may be advisable.