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FIFO(7)			   Linux Programmer's Manual		       FIFO(7)

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

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

       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 nonblocking	mode.  In this	case,  opening
       for  read-only will succeed even	if no-one has opened on	the write side
       yet, opening for	write-only will	fail with ENXIO	(no such device	or ad-
       dress) unless the other end has already been opened.

       Under  Linux,  opening  a  FIFO for read	and write will succeed both in
       blocking	and nonblocking	mode.  POSIX leaves this  behavior  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.

       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 indicated by ls
       -l with the file	type 'p'.

       mkfifo(1),  open(2),  pipe(2),  sigaction(2), signal(2),	socketpair(2),
       mkfifo(3), pipe(7)

       This page is part of release 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at

Linux				  2008-12-03			       FIFO(7)


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