popd

popd is a command line tool commonly used in Unix-based systems to manipulate the shell's working directory. It is used to remove a directory from the directory stack and change the current working directory to the one that was popped.

When used without any arguments, popd removes the topmost directory from the stack and changes the current working directory to the second topmost directory. It essentially undoes the action performed by the pushd command.

The directory stack is a LIFO (last in, first out) stack that keeps track of directories. Each time a directory is pushed onto the stack using the pushd command, the current working directory is changed to the directory being pushed.

popd supports several options and functionalities. For example, using the "-n" option prevents the actual change of the current directory when popping a directory. With the "-q" option, the output messages are suppressed. The "-" option swaps the top two directories on the stack, effectively toggling between them.

By default, popd displays the new current working directory after popping a directory. This behavior can be modified using the "-s" option, which suppresses the output display.

If the directory stack is empty, popd throws an error. However, an empty directory stack is not an invalid state, since the directories are only pushed onto the stack when explicitly requested.

The command popd is commonly used in scripting and automation tasks to navigate between different directories and maintain a history of visited directories. It simplifies directory management and allows users to easily switch between frequently accessed directories.