Rules for Naming and Accessing Files

The rules for naming and accessing files and directories are closely related to the structure of the Unix file system:

• The root directory is identified by a slash (/).
• A simple filename can be any combination of 1 - 14 characters other than slashes (/), asterisks (*), question marks (?), quotation marks (`` ) or ('), square brackets ([) or (]), dollar sign ($) or control characters.
• A path name is a sequence of directory names, possibly followed by a simple filename, with each name separated by a slash (/).

To avoid misinterpretation, the safest characters to use for simple filenames are letters of the alphabet, numbers, periods (.), hyphens (-), and underline (_). Note: in Unix, upper and lower case are not the same. Examples could include --

 
               		   /usr/local/bin

               		   long-description-name

               		   mydoc.ps

               		   myfile.f

               		   /afs/cern.ch/user/f/fred/public/shared.info

The directory permanently assigned to you is called your home directory; this is the directory in which you are placed when you log on. Any directory to which you move after logging on (including your home directory) will be called your current directory, or working directory or cwd, for as long as you remain in that directory. The directory which is one level above your current directory in the file system is called your parent directory. Unix provides shorthand symbols to indicate your current directory (.) and your parent directory (..). If a path name used to access a file begins with a slash (/), then the search for the file begins at the root directory. Such a path name is called an absolute path name  or full path name. If a path name begins with a simple filename, then the search for the file begins at your current directory. Such a path name is called a relative path name .