Why are unquoted variables (SC2086) dangerous in Bash?

When variables like $filename are unquoted, spaces or wildcard characters inside the value trigger word splitting and filename globbing. This can cause commands like rm -rf $DIR to delete unexpected directories if DIR is empty or contains spaces.

Why should backticks be replaced with $()?

Legacy backticks do not nest easily without complicated backslash escaping and make scripts harder to read. The modern $(command) syntax is standard POSIX and supports arbitrary nested subshells.

Bash Script Linter & ShellCheck Advisor

Analyze Bash, sh, and Zsh scripts for silent bugs, globbing vulnerabilities, unquoted expansion pitfalls, and non-portable idioms. 100% offline in your browser.

Script Health 100%

Errors 0

Warnings 0

Style Hints 0

SHELL SCRIPT INPUT 0 lines

SHELLCHECK-EQUIVALENT ISSUES 0 issues

Click "Lint Script" to analyze shell code.

Frequently Asked Questions

What rules are checked?

This linter evaluates key rules: SC2086 (double quote to prevent globbing/word splitting), SC2006 (replace legacy backticks with $(...)), SC2002 (useless cat), SC2164 (use cd ... || exit), SC2181 (check exit status directly rather than $?), and SC2155 (declare and assign separately).

Can this tool execute my script?

No. This tool is a static analyzer that operates entirely through pattern inspection and lexical rules. It never executes your commands or touches your filesystem.