ShellCheck

ShellCheck is a GPLv3 tool that provides warnings and possible suggestions for bash/sh shell scripts. ShellCheck finds bugs in your shell scripts. You can cabal, apt, dnf, pkg or brew install it locally right now. ShellCheck highlights and clarifies typical beginner's syntax mistakes and issues that cause a shell to give a cryptic error message. It shows typical intermediate level semantic problems that cause a shell to behave in a abnormally and counter-intuitively. It can also discover ssubtle caveats, corner cases and pitfalls that may cause an user's working script to fail under probable future circumstances. ShellCheck.net is always synchronized to the latest git version, and is the simplest way to give ShellCheck a go.