NAME | DESCRIPTION | NOTES | SEE ALSO | COLOPHON
FIFO(7) Linux Programmer's Manual FIFO(7)
fifo - first-in first-out special file, named pipe
A FIFO special file (a named pipe) is similar to a pipe, except that it is
accessed as part of the file system. 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 file system.
Thus, the FIFO special file has no contents on the file system; the file
system entry merely serves as a reference point so that processes can access
the pipe using a name in the file system.
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 non-blocking mode. In this case, opening for
read only will succeed even if no-one has opened on the write side yet,
opening for write only will fail 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 non-blocking 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.
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'.
mkfifo(1), open(2), pipe(2), sigaction(2), signal(2), socketpair(2),
mkfifo(3), pipe(7)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-12-03 FIFO(7)