Update cheatsheets

shellcheck

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# shellcheck
+
+> Shell script static analysis tool.
+> Check shell scripts for errors, usage of deprecated/insecure features, and bad practices.
+> More information: <https://www.shellcheck.net>.
+
+- Check a shell script:
+
+`shellcheck {{path/to/script.sh}}`
+
+- Check a shell script interpreting it as the specified shell dialect (overrides the shebang at the top of the script):
+
+`shellcheck --shell {{sh|bash|dash|ksh}} {{path/to/script.sh}}`
+
+- Ignore one or more error types:
+
+`shellcheck --exclude {{SC1009,SC1073}} {{path/to/script.sh}}`
+
+- Also check any sourced shell scripts:
+
+`shellcheck --check-sourced {{path/to/script.sh}}`
+
+- Display output in the specified format (defaults to `tty`):
+
+`shellcheck --format {{tty|checkstyle|diff|gcc|json|json1|quiet}} {{path/to/script.sh}}`
+
+- Enable one or more optional checks:
+
+`shellcheck --enable={{add-default-case|avoid-nullary-conditions}}`
+
+- List all available optional checks that are disabled by default:
+
+`shellcheck --list-optional`