Using named pipes (FIFO) to inter process communication (IPC) in c++

 Named pipes can be used, if you need to setup a bidirectional channel between two processes.

Traditional UNIX pipe is unnamed and it lasts only during the process lifetime, where as named pipes last as long as the system is up, beyond the life of the process.

A named pipe is basically a file and converted into a FIFO using mkfifo(). 

Then processes attach to it for reading/writing purpose. After that reading and writing can be done as on a regular file in C++.

There have to be reading process "attached" for the other side of the pipe. If you try to open pipe for writing and there is no reading process, open will hang waiting for it or return -1 with errno set to ENXIO (when O_NONBLOCK flag is used)

NOTE:

Pipes are byte-oriented, not message oriented. If you want messages, there's other IPC for that (e.g., SysV message queues).

Since it is a stream of bytes we may need to establish a minimal transport protocol (for example use '\0' byte as a delimiter, Number of bytes write/read form sender/reciever)