1FIFO(7) Linux Programmer's Manual FIFO(7)
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6 fifo - first-in first-out special file, named pipe
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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.
16 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.
21 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.
26 Under Linux, opening a FIFO for read and write will succeed both in
28 blocking and non-blocking mode. POSIX leaves this behaviour 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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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.
36 FIFO special files can be created by mkfifo(3), and are specially indi‐
38 cated in ls -l.
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41 mkfifo(1), open(2), pipe(2), sigaction(2), signal(2), socketpair(2),
42 mkfifo(3), pipe(7)
43Linux 1999-06-20 FIFO(7)