What command is used to find a file by name in the filesystem?

The command used to find a file by name in the filesystem is "locate". This command searches through a pre-built database of filenames and quickly returns results, which makes it efficient for finding files. The database is typically updated daily or can be updated manually using the "updatedb" command.

While "find" is another common command for searching files, it differs because it searches the filesystem in real-time rather than referencing a database, which can be slower. "search" is not a standard command in most Linux distributions for locating files, making it an incorrect choice, and "grep" is used to search through the contents of files for specific patterns rather than for filenames in the filesystem. Therefore, "locate" stands out as the most suitable command for quickly finding files by name.