The goals of ShellCheck are

• To point out and clarify typical beginner's syntax issues that cause a shell to give cryptic error messages.
• To point out and clarify typical intermediate level semantic problems that cause a shell to behave strangely and counter-intuitively.
• To point out subtle caveats, corner cases and pitfalls that may cause an advanced user's otherwise working script to fail under future circumstances.

See the gallery of bad code for examples of what ShellCheck can help you identify!

ShellCheck is...

• GPLv3: free as in freedom
• available on GitHub
• already packaged for your distro or package manager
• supported as an integrated linter in major editors
• available in CodeClimate, Codacy and CodeFactor to auto-check your GitHub repo
• written in Haskell, if you're into that sort of thing.