Korn Shell Programming by Example

Special Files

My first experiences with UNIX were as a C programmer. I was familiar with writing programs for low-level access to devices for reads or writes, or getting or setting device characteristics, but had never done it in UNIX. I had always done this by opening a channel to the device and using functions that run in kernel mode (referred to as system calls or system services) to get or set what I wanted. I figured I could do the same kind of thing in UNIX, but I didn't know how. I spoke with a new hire who had UNIX experience and asked him how to perform low-level I/Os to a device in UNIX. He thought for a few seconds and said, “Well, that's easy. You just open a file. Everything in UNIX is represented by a file.”

I thanked him and backed ...