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ShellCheck Error Decoder

Quick Answer

ShellCheck analyzes bash scripts for mistakes that work on happy-path input but fail on edge cases — unquoted variables, unreachable commands, deprecated syntax, and pipelines that hide errors. SC2086 alone appears in thousands of production scripts: an unquoted `$var` splits on whitespace and expands globs, breaking filenames with spaces. Reading the raw rule text in terminal output requires context switching between the error code, the wiki, and your editor. This decoder accepts any SC code such as SC2086, returns the rule name, a plain-English explanation of what is wrong, why it matters in production, and a before/after code example showing the fix. Click Copy Fix to paste the corrected line directly. Use it during code review, while clearing CI ShellCheck gates, or when onboarding juniors who need the rationale behind each warning, not just the flag name. Lookup runs client-side with no login. Fixing warnings before deploy prevents the exact failures ShellCheck was designed to catch — silent breakage on unexpected input.

How to use the ShellCheck Error Decoder

  1. 1Paste a ShellCheck error code (e.g., SC2086) into the search field, or type the four-digit number directly.
  2. 2The tool displays the full rule name, a plain-English explanation of what is wrong, and why it matters.
  3. 3Review the before/after code example to see exactly what change ShellCheck expects.
  4. 4Click "Copy Fix" to get the corrected line for your script, then run ShellCheck again to confirm the warning is resolved.

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Frequently Asked Questions

faq — tool

What is ShellCheck?

ShellCheck is an open-source static analysis tool for bash and sh scripts. It detects common mistakes — unquoted variables, incorrect conditionals, portability issues, and deprecated syntax — before they cause failures in production. It is available as a CLI tool and integrates with most editors.

faq — tool

How do I run ShellCheck on my script?

Install ShellCheck with `apt install shellcheck` on Debian/Ubuntu or `brew install shellcheck` on macOS. Then run `shellcheck script.sh`. For CI pipelines, ShellCheck exits non-zero if any warnings are found, making it easy to enforce as a gate.

faq — tool

What does ShellCheck SC2086 mean?

SC2086 warns that a variable is not double-quoted, which exposes it to word splitting and glob expansion. `echo $var` should be `echo "$var"`. If $var contains spaces or special characters, the unquoted version breaks silently in ways that are hard to debug.

faq — tool

Why does ShellCheck flag my script if it works fine?

ShellCheck warns about patterns that work in normal cases but fail in edge cases — variables with spaces, filenames with special characters, or pipelines that swallow errors. Each warning is a real bug risk. The script appears to work until it encounters unexpected input.

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