In this section, we learned about:

• Heredocs and here strings, and their similarities and differences.
• Using the printf command to do string interpolation.
• Using brace expansion to combine several similar commands into one line of code.
• Importing files via the source command, and the difference between source foo and ./foo.
• How to escape code within strings using the \ escape character.
• What escape characters are, and why they’re used.
• Some very basic syntax of non-Bash shells:
  • How to declare a local variable in fish and ksh.
  • Accessing the arguments passed to a fish shell script via argv[].
  • How to declare local variables in a fish script using the set command.
  • How to print a function definition in fish using the functions command.
  • How to evaluate fish code inside the current process context using the source command.
  • The difference between set -e in fish vs. Bash
  • How the function keyword is optional in Bash and zsh, but not in fish or ksh.
• Why you might not want to use the function keyword in your Bash or zsh shells.
• How to set a default value in a parameter expansion using :-.
• Why the core team was unsatisfied with RVM’s approach of overriding the cd command, and decided to make shell integration optional in RBENV.
• The pros and cons of using Bash, zsh, fish, and ksh, and why you might pick one over the others.