Shell tools : shellcheck

• ShellCheck, a static analysis tool for shell scripts

https://github.com/koalaman/shellcheck

• https://steinbaugh.com/posts/posix.html lists some 
• => https://steinbaugh.com/posts/posix.html#conditional-expressions
• => https://steinbaugh.com/posts/posix.html#parameter-expansion

• https://www.grymoire.com/Unix/Sh.html

• https://jjasghar.github.io/blog/2019/06/15/shellcheck-and-you-should-too/

suggests to add this on your makefiles :

check-scripts:
    # Fail if any of these files have warnings
    shellcheck myscripts/*.sh

or this on your CI (here : .travis.yml )

script:
  # Fail if any of these files have warnings
  - shellcheck myscripts/*.sh