What is the command used to remove empty directories?

The command utilized to remove empty directories in a Linux environment is rmdir. This command effectively deletes directories but only if they are empty; if the directory contains files or other directories, the command will not execute and will instead return an error message. This functionality is particularly useful for maintaining a clean directory structure by ensuring that no empty directories remain.

In contrast, the other commands listed have different purposes. updatedb is used to update the database of files for the locate command, primarily for quick file searches. tr is a command-line utility intended for translating or deleting characters from standard input. Meanwhile, paste is used for merging lines of files. Understanding the specific uses of these commands highlights why rmdir is the appropriate choice for removing empty directories.