FIFO(4) 						     Linux Programmer's Manual							   FIFO(4)

NAME

       fifo - first-in first-out special file, named pipe

DESCRIPTION

       A FIFO special file (a named pipe) is similar to a pipe, except that it is accessed as part of the file system.	It can be opened by multi-
       ple processes for reading or writing. When processes are exchanging data via the FIFO, the kernel passes all data internally without  writ-
       ing  it to the file system. Thus, the FIFO special file has no contents on the file system, the file system entry merely serves as a refer-
       ence point so that processes can access the pipe using a name in the file system.

       The kernel maintains exactly one pipe object for each FIFO special file that is opened by at least one process.	The FIFO must be opened on
       both ends (reading and writing) before data can be passed. Normally, opening the FIFO blocks until the other end is opened also.

       A process can open a FIFO in non-blocking mode. In this case, opening for read only will succeed even if noone has opened on the write side
       yet; opening for write only will fail with ENXIO (no such device or address) unless the other end has already been opened.

       Under Linux, opening a FIFO for read and write will succeed both in blocking and non-blocking mode. POSIX leaves this behaviour	undefined.
       This  can be used to open a FIFO for writing while there are no readers available. A process that uses both ends of the connection in order
       to communicate with itself should be very careful to avoid deadlocks.

NOTES

       When a process tries to write to a FIFO that is not opened for read on the other side, the process is sent a SIGPIPE signal.

       FIFO special files can be created by mkfifo(3), and are specially indicated in ls -l.

SEE ALSO

       mkfifo(3), mkfifo(1), pipe(2), socketpair(2), open(2), signal(2), sigaction(2)

Linux Man Page							    1999-06-20								   FIFO(4)