fifo(7)                                           Miscellaneous Information 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 behav‐
       ior  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 man-pages 6.03                                         2023-02-05                                                     fifo(7)