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 file system.  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 file system.  Thus, the FIFO special file has no contents on the
14       file system; the file system entry merely serves as a  reference  point
15       so that processes can access the pipe using a name in the file system.
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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 non-blocking mode.  In this case,  opening
23       for  read only will succeed even if no-one has opened on the write side
24       yet, opening for write only will fail with ENXIO  (no  such  device  or
25       address) 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 non-blocking 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       When  a process tries to write to a FIFO that is not opened for read on
35       the other side, the process is sent a SIGPIPE signal.
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37       FIFO special files can be created by mkfifo(3), and are indicated by ls
38       -l with the file type 'p'.
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SEE ALSO

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

45       This page is part of release 3.22 of the Linux  man-pages  project.   A
46       description  of  the project, and information about reporting bugs, can
47       be found at http://www.kernel.org/doc/man-pages/.
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51Linux                             2008-12-03                           FIFO(7)
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