SC2148 – ShellCheck Wiki

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Tips depend on target shell and yours is unknown. Add a shebang.

Problematic code:

echo "$RANDOM"   # Does this work?

Correct code:

echo "$RANDOM"  # Unsupported in sh. Produces warning.


echo "$RANDOM"  # Supported in bash. No warnings.


Different shells support different features. To give effective advice, ShellCheck needs to know which shell your script is going to run on. You will get a different numbers of warnings about different things depending on your target shell.

If you add a shebang (e.g. #!/bin/bash as the first line), the OS will use this interpreter when the script is executed, and ShellCheck will use this shell when offering advice.

If you for any reason can't or won't add a shebang, there are multiple other ways to let shellcheck know which shell you're coding for:


None. Please either add a shebang, directive, extension or use -s to maximize ShellCheck's usefulness.

ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.