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)

Linux man-pages 6.7                                2023-10-31                                            fifo(7)