fifo(7) - Linux manual page (original) (raw)

fifo(7) Miscellaneous Information Manual fifo(7)

NAME top

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

DESCRIPTION top

   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 top

   For details of the semantics of I/O on FIFOs, see [pipe(7)](../man7/pipe.7.html).

   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)](../man3/mkfifo.3.html), and are indicated
   by _ls -l_ with the file type 'p'.

SEE ALSO top

   [mkfifo(1)](../man1/mkfifo.1.html), [open(2)](../man2/open.2.html), [pipe(2)](../man2/pipe.2.html), [sigaction(2)](../man2/sigaction.2.html), [signal(2)](../man2/signal.2.html),
   [socketpair(2)](../man2/socketpair.2.html), [mkfifo(3)](../man3/mkfifo.3.html), [pipe(7)](../man7/pipe.7.html)

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Linux man-pages 6.10 2024-05-02 fifo(7)

Pages that refer to this page:open(2), mkfifo(3), sd_is_fifo(3), systemd.socket(5), pipe(7), signal(7)