unset

The unset command line tool is used in Unix-like operating systems to remove or unset shell variables and functions. It allows the user to delete specific variables or functions set within the shell environment.

When used without any arguments, unset does not have any effect. However, when followed by a variable name, it will remove that specific variable from the shell environment. For example, unset MY_VAR will unset the variable MY_VAR.

The unset command can also be used with multiple variable or function names, separated by spaces, to unset multiple variables/functions in one command. For instance, unset VAR1 VAR2 will unset both VAR1 and VAR2.

Additionally, you can use the -v flag with unset to unset variables only, while functions will be left untouched. This can be useful when dealing with a mixture of variables and functions.

The effects of unset are not permanent, as it only affects the current shell environment. Once the shell is closed or a new session is started, the variables or functions that have been unset will no longer be affected.

It is worth noting that unsetting a variable does not free up any memory; it merely removes the association of the variable name with its value.

Using unset incorrectly or without proper caution can lead to unintended consequences, such as breaking scripts or causing unexpected behavior in the shell environment.