Pattern: Use of ! -z
instead of -n
Issue: -
You have negated test -z
or test -n
, resulting in a needless double-negative. You can just use the other operator instead:
# Identical tests to verify that a value is assigned
[ ! -z foo ] # Not has no value
[ -n foo ] # Has value
# Identical tests to verify that a value is empty
[ ! -n foo ] # Not is non-empty
[ -z foo ] # Is empty
Example of incorrect code:
if [ ! -n "$JAVA_HOME" ]; then echo "JAVA_HOME not specified"; fi
if [ ! -z "$STY" ]; then echo "You are already running screen"; fi
Example of correct code:
if [ -z "$JAVA_HOME" ]; then echo "JAVA_HOME not specified"; fi
if [ -n "$STY" ]; then echo "You are already running screen"; fi
This is a stylistic issue that does not affect correctness. If you prefer the original expression, you can ignore it with a directive or flag.