How To: Temporarily Clear Bash Environment Variables on a Linux and Unix-like System

To temporarily clear environment variables on a Linux or Unix-like system, you can use the unset command in a subshell.

A subshell is a child process that is created to execute a command or a set of commands. The environment of the subshell is inherited from the parent shell, but any changes made to the environment within the subshell do not affect the parent shell.

To create a subshell and clear environment variables within it, you can use the following syntax:

(unset <variable>; <command>)

For example, to clear the FOO environment variable and run the ls command in a subshell, you can use the following command:

(unset FOO; ls)

This will unset the FOO variable in the subshell and then run the ls command. When the subshell exits, the FOO variable will be restored to its original value in the parent shell.

You can also use the unset command to clear multiple environment variables at once. For example:

(unset FOO BAR BAZ; ls)

This will clear the FOO, BAR, and BAZ variables in the subshell and then run the ls command.

Keep in mind that the unset command only affects the environment variables of the subshell. It does not affect the environment variables of the parent shell or any other processes.

You can also use the env -i command to create a new, empty environment and run a command in it. This can be useful if you want to completely clear the environment and start with a fresh set of variables.

For example:

env -i ls

This will create a new, empty environment and run the ls command in it. All of the environment variables from the parent shell will be ignored.