1FIFO(7)                    Linux Programmer's Manual                   FIFO(7)
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NAME

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

9       A FIFO special file (a named pipe) is similar to a pipe, except that it
10       is accessed as part of the filesystem.  It can be  opened  by  multiple
11       processes  for  reading or writing.  When processes are exchanging data
12       via the FIFO, the kernel passes all data internally without writing  it
13       to  the filesystem.  Thus, the FIFO special file has no contents on the
14       filesystem; the filesystem entry merely serves as a reference point  so
15       that processes can access the pipe using a name in the filesystem.
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17       The kernel maintains exactly one pipe object for each FIFO special file
18       that is opened by at least one process.  The FIFO  must  be  opened  on
19       both  ends  (reading and writing) before data can be passed.  Normally,
20       opening the FIFO blocks until the other end is opened also.
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22       A process can open a FIFO in nonblocking mode.  In this  case,  opening
23       for  read-only succeeds even if no one has opened on the write side yet
24       and opening for write-only fails with ENXIO (no such device or address)
25       unless the other end has already been opened.
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27       Under  Linux,  opening  a  FIFO for read and write will succeed both in
28       blocking and nonblocking mode.  POSIX leaves this  behavior  undefined.
29       This  can be used to open a FIFO for writing while there are no readers
30       available.  A process that uses both ends of the connection in order to
31       communicate with itself should be very careful to avoid deadlocks.
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NOTES

34       For details of the semantics of I/O on FIFOs, see pipe(7).
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36       When  a process tries to write to a FIFO that is not opened for read on
37       the other side, the process is sent a SIGPIPE signal.
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39       FIFO special files can be created by mkfifo(3), and  are  indicated  by
40       ls -l with the file type 'p'.
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SEE ALSO

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

47       This page is part of release 5.12 of the Linux  man-pages  project.   A
48       description  of  the project, information about reporting bugs, and the
49       latest    version    of    this    page,    can     be     found     at
50       https://www.kernel.org/doc/man-pages/.
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54Linux                             2017-11-26                           FIFO(7)
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