Shell Script Linter

The linter catches common Bash/shell script problems including: unquoted variables (word splitting/globbing risk), use of backticks instead of $(), ls used for file listing (unsafe), useless cat (UUOC), missing set -e/-u at the top, rm -rf without guards, == vs = in [ ] tests, and function keyword portability issues.

SC2086 is the ShellCheck rule for unquoted variables. When you write $var instead of "$var", the shell performs word splitting and glob expansion on the value. This means a variable containing spaces or wildcards can break your command in unexpected ways. Always quote: echo "$filename" not echo $filename.

Backtick command substitution (`cmd`) is harder to read, can't be nested easily, and has different escaping rules. The $() form is cleaner, nestable ($(outer $(inner))), and universally supported in modern shells. ShellCheck labels this SC2006.

-e makes the script exit immediately if any command fails. -u treats unset variables as errors. -o pipefail makes pipelines fail if any command in the pipe fails (not just the last one). Together, these three options turn your script into a much safer, fail-fast mode that catches bugs earlier.

In Bash, prefer [[ ]] over [ ] for conditionals. Double brackets support == for string comparison, && and || inside the test, regex matching with =~, and don't require quoting in most cases. Single brackets [ ] follow POSIX rules: use = not ==, and always quote variables.

ls output is not designed for programmatic parsing. Filenames can contain newlines, spaces, or special characters that break ls output. Use find with -name for filtering: find . -name '*.log'. This safely handles all filename edge cases.