shellcheck

Check a shell script

$ shellcheck [script.sh]

$ shellcheck [script1.sh] [script2.sh]

$ shellcheck --shell=[bash|sh|dash|ksh] [script.sh]

$ shellcheck --format=[json|gcc|checkstyle] [script.sh]

$ shellcheck --exclude=[SC2034,SC2086] [script.sh]

$ cat [script.sh] | shellcheck -

$ shellcheck --enable=all [script.sh]

shellcheck [options] [script...]

shellcheck is a static analysis tool for shell scripts. It detects bugs, syntax issues, and pitfalls in bash/sh/ksh/dash scripts, providing explanations and suggestions for fixes.
Each warning has a code (e.g., SC2086) linking to detailed wiki documentation explaining the issue, why it matters, and how to fix it. This makes shellcheck excellent for learning shell scripting best practices.
The tool catches common issues like unquoted variables, deprecated syntax, command substitution pitfalls, and potential security vulnerabilities. It distinguishes between different shell dialects and their specific features.
Integration is available for most editors (VS Code, Vim, Emacs, Sublime) and CI systems, enabling automated script checking.

-s, --shell dialect

Specify shell dialect (sh, bash, dash, ksh)

Output format (tty, gcc, json, checkstyle, diff, quiet)

Exclude specific error codes (comma-separated)

Include only specific error codes

Enable optional checks (all, require-variable-braces, etc.)

Enable specific optional checks

Follow and check sourced files

Check sourced files for issues

Minimum severity (error, warning, info, style)

Display version

Include wiki links for first n warnings

SC2086: Double quote to prevent globbing and word splitting
SC2034: Variable appears unused
SC2046: Quote to prevent word splitting
SC2006: Use $(...) instead of backticks
SC2035: Use ./\* so patterns don't expand to options
SC2164: Use cd ... || exit in case cd fails

ShellCheck may produce false positives when variables are used indirectly or sourced from external files. Use # shellcheck disable=SC#### comments to suppress specific warnings.
Some legitimate shell patterns trigger warnings. Review each warning before disabling; often the suggested fix is genuinely better.
The --external-sources option requires caution as it can execute arbitrary code when checking scripts that source files.

bash(1), sh(1), lint(1)