Double-Quotes

When shell encounters a double-quote ("), it starts creating a string using these rules:

1. Another double-quote ends the contents but can be escapaed (e.g., "I said, \"Hello.\"")

2. Escape sequences are expanded (e.g., \t may be translated into a literal TAB)

3. Variables are expanded (e.g., $foo becomes contents of foo variable)

4. Command substitutions are performed (e.g., $(date) and `date` become the output of date command)

For example:

1 #!/bin/sh
2 person=Joe
3 echo "I heard from $person that \"$(date +%Y) is the year of ...,\" but I am doubtful."

Produces:

I heard from Joe that "2017 is the year of ...," but I am doubtful.