Pattern: Possibly dangerous use of "$empty/"
Issue: -
This rule is indented to detect some catastrophic rm -r "$empty/" mistakes.
Example of incorrect code:
rm -rf "$STEAMROOT/"*If STEAMROOT is empty, this will end up deleting everything in the system's root directory.
Using :? will cause the command to fail if the variable is null or unset. Similarly, you can use :- to set a default value if applicable.
In the case command substitution, assign to a variable first and then use :?. This is relevant even if the command seems simple and obviously correct, since forks and execs can fail due to external system limits and conditions, resulting in a blank substitution.
Example of correct code:
rm -rf "${STEAMROOT:?}/"*