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

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 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 file system.  Thus, the FIFO
       special file has no contents on the file system; the file system entry merely serves as a  reference  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
       no-one 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 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.

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

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

COLOPHON
       This page is part of release 3.15 of the Linux man-pages project.  A description of the project, and infor-
       mation about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

Linux                                               2008-12-03                                             FIFO(7)