Pipes and FIFOs are both forms of queues that connect processes.
Note:
In order for you to use pipes or FIFOs in the
QNX Neutrino RTOS, the pipe
resource manager
(
pipe)
must be running.
- Pipes
- A pipe is an unnamed file that serves as an I/O
channel between two or more cooperating processes: one
process writes into the pipe, the other reads from the pipe.
The pipe manager takes care of buffering the
data. The buffer size is defined as PIPE_BUF
in the <limits.h> file. A pipe is removed
once both of its ends have closed. The function
pathconf()
returns the value of the limit.
Pipes are normally used when two processes want to run in
parallel, with data moving from one process to the other in
a single direction. (If bidirectional communication is
required, messages should be used instead.)
A typical application for a pipe is connecting the output of
one program to the input of another program. This connection
is often made by the shell. For example:
ls | more
directs the standard output from the ls utility
through a pipe to the standard input of the more
utility.
| If you want to: |
Use the: |
| Create pipes from within the shell |
pipe symbol (“|”) |
| Create pipes from within programs |
pipe()
or
popen() functions
|
- FIFOs
- FIFOs are essentially the same as pipes, except that FIFOs
are named permanent files that are stored in filesystem directories.
| If you want to: |
Use the: |
| Create FIFOs from within the shell |
mkfifo utility |
| Create FIFOs from within programs |
mkfifo() function |
| Remove FIFOs from within the shell |
rm utility |
| Remove FIFOs from within programs |
remove()
or
unlink() function |