7.1 dir dir is available on the campus Unix systems, and provides a similar display to that of the MS-DOS dir command. This is not an inherent part of Unix and should not be expected on other systems. Use ls -la to see all of the available information about a directory or about files. Files are simply named. The find command enables you to search through one or more directories for a file with a specific name, which can also be described with a regular expression .
Regular expression is a technical term for specific way of describing a string of characters.
A regular expression is a notation for specifying and matchings strings. Like an arithmetic expression, a regular expression is a basic expression or one created by applying operators to compponent expressions. The complete file name happens to include the full path to that file, so even though there may be multiple files called xxxx , they can be differentiated using their actual directory paths.