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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 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 succeeds even if no one has opened on the write side yet
       and opening for write-only fails 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 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.
NOTES
       For details of the semantics of I/O on FIFOs, see pipe(7).
       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 4.15 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
       https://www.kernel.org/doc/man-pages/.
Linux                             2017-11-26                           FIFO(7)