How Linux Works

Subshells

Sometimes you need to alter the environment in a shell slightly, but don't want a permanent change. You can change and restore a part of the environment (such as the path or working directory) using shell variables, but that is a clumsy way to go about things. The easy way around these kinds of problems is to use a subshell, an entirely new shell process that you can create just for the purpose of running a command or two. The new shell has a copy of the original shell's environment, and when the new shell exits, any changes you made to its shell environment disappear, leaving the initial shell to run as normal.

To use a subshell, put the commands to be executed by the subshell in parentheses. For example, the following line executes ...