44.7. FIFOs

Semantically, a FIFO is similar to a pipe. The principal difference is that a FIFO has a name within the file system and is opened in the same way as a regular file. This allows a FIFO to be used for communication between unrelated processes (e.g., a client and server).

Once a FIFO has been opened, we use the same I/O system calls as are used with pipes and other files (i.e., read(), write(), and close()). Just as with pipes, a FIFO has a write end and a read end, and data is read from the pipe in the same order as it is written. This fact gives FIFOs their name: first in, first out. FIFOs are also sometimes known as named pipes.