Devices in a Network Environment

In a Unix file system, the input/output devices, such as, terminals, printers, tape, and disk drives, are referenced as files in the directory tree which contains the names of all the files in the file system. All devices are usually located in the /dev directory. For example, a terminal device can be accessed by referencing a name usually of the form ttyn where n is some number. If an application wishes to read or write to a terminal device, it uses the name /dev/ttyn as the pathname argument to Unix I/O functions.

Some file systems may not be able to support devices as part of a the file system's directory tree. For those file systems that can support devices, the use of a terminal device as a controlling terminal may not be supported. In a network environment, where an application may have access to several different file systems, the application should be able to obtain the following information associated with devices:

• Whether the file system supports devices.
• If devices are supported, whether the physical location of the device, i.e., the system to which the device is physically attached, is the local system or a server.
• If devices are supported, whether a particular terminal device can become a controlling terminal.
• If devices are supported, whether the location of the device file, i.e., where the inode resides, is on the local system or a server.