fifo(7) — Linux manual page


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

       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).

       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         top

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

Linux man-pages (unreleased)     (date)                          fifo(7)

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