unset.sh

Shall高级编程

#!/bin/bash
# unset.sh: Unsetting a variable.

variable=hello                       # Initialized.
echo "variable = $variable"

unset variable                       # Unset.
                                     # Same effect as:  variable=
echo "(unset) variable = $variable"  # $variable is null.

if [ -z "$variable" ]                # Try a string-length test.
then
  echo "\$variable has zero length."
fi

exit 0