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Annotated edit history of fifo(4) version 2, including all changes. View license author blame.
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1 perry 1 FIFO
2 !!!FIFO
3 NAME
4 DESCRIPTION
5 NOTES
6 SEE ALSO
7 ----
8 !!NAME
9
10
11 fifo - first-in first-out special file, named pipe
12 !!DESCRIPTION
13
14
15 A FIFO special file (a named pipe) is similar to a pipe,
16 except that it is accessed as part of the file system. It
17 can be opened by multiple processes for reading or writing.
18 When processes are exchanging data via the FIFO, the kernel
19 passes all data internally without writing it to the file
20 system. Thus, the FIFO special file has no contents on the
21 file system, the file system entry merely serves as a
22 reference point so that processes can access the pipe using
23 a name in the file system.
24
25
26 The kernel maintains exactly one pipe object for each FIFO
27 special file that is opened by at least one process. The
28 FIFO must be opened on both ends (reading and writing)
29 before data can be passed. Normally, opening the FIFO blocks
30 until the other end is opened also.
31
32
33 A process can open a FIFO in non-blocking mode. In this
34 case, opening for read only will succeed even if noone has
35 opened on the write side yet; opening for write only will
36 fail with ENXIO (no such device or address) unless the other
37 end has already been opened.
38
39
40 Under Linux, opening a FIFO for read and write will succeed
41 both in blocking and non-blocking mode. POSIX leaves this
42 behaviour undefined. This can be used to open a FIFO for
43 writing while there are no readers available. A process that
44 uses both ends of the connection in order to communicate
45 with itself should be very careful to avoid
46 deadlocks.
47 !!NOTES
48
49
2 JohnDoe 50 When a process tries to write to a FIFO that is not opened anymore
1 perry 51 for read on the other side, the process is sent a SIGPIPE
52 signal.
53
2 JohnDoe 54 In general, if you close and re-open one side you need to do it on the other side, too. ''(Is this correct?)''
1 perry 55
56 FIFO special files can be created by mkfifo(3), and
57 are specially indicated in ''ls -l''.
58 !!SEE ALSO
59
60
61 mkfifo(3), mkfifo(1), pipe(2),
62 socketpair(2), open(2), signal(2),
63 sigaction(2)
64 ----
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