What does the command `unset VARIABLE_NAME` do in bash?

The command unset VARIABLE_NAME in bash is used to delete the specified variable completely from the environment. This means that after executing this command, the variable will no longer exist in the shell. It removes both the variable and its associated value, ensuring that any subsequent attempts to reference that variable will result in an error or an empty result.

When a variable is unset, it is as if the variable was never created in the first place, which is particularly useful in scripts where the existence of variables can affect logic and flow. This command is commonly used for cleanup purposes, especially when a variable is no longer needed, helping to avoid conflicts or accidental use later on.

Other options do not capture the full functionality of the unset command. For instance, simply removing the variable's value does not affect the variable's existence, and setting a variable to zero would assign a new value rather than deleting it altogether. Displaying the variable's current value is unrelated since the unset command does not produce any output regarding existing values.