Update bash-commands to mostly conform to SC1117.
Update bash-commands to mostly conform to SC1117.

Escape backslashes to explitly pass them as literal backslashes.

ShellCheck SC1117
https://github.com/koalaman/shellcheck/wiki/SC1117

Backslashes in the help `HEREDOC` have not been updated. The program is
currently encountering errors on at least one recent Bash version, so
the current escaping is being retained in this `HEREDOC` until it can be
tested.

alphabetum/bash-boilerplate