FIFOs (named pipes)

FIFOs (named pipes)

Reference: More details are in Section 14.5, Advanced Programming in the UNIX Environment, by W. Richard Stevens.

FIFOs are used for piping data between unrelated processes or if a entry for a pipe is needed in the file system. FIFOs are entries in the file system (that's why they are called named!) that behave like pipes - they can be written to and read from. Access is governed as usual for files.

An example of a FIFO is Solaris's /var/spool/lp/fifos/FIFO which is used by lp to receive print requests. In an ls listing they appear with a p to indicate pipe and a | is appended to the name if ls -F is used:

prw-rw-rw- 1 lp lp 0 Jun 19 1998 FIFO|

FIFOs can be created with the shell command mkfifo or the system call mkfifo( ). These in turn invoke the system call mknod( ) which can be used directly. The shell command mknod filename p may be used instead. mknod is the command for making a special file (a device file).

Last update: 2000 December 28