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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 read‐
       ing 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)

Linux                                                                          2017-11-26                                                                        FIFO(7)