Named Pipes (FIFOs) on Unix with multiple readers

Question

I have two programs, Writer and Reader.

I have a FIFO from Writer to Reader so when I write something to stdin in Writer, it gets printed out to stdout from Reader.

I tried doing this with TWO Readers open, and I got output to stdout from only one of the two Reader programs. Which Reader program Unix chooses to print stdout from seemed to be arbitrary each time I run this, but once it chooses one of the programs, each output to stdout gets printed from the same Reader program.

Does anyone know why this happens?

If I have two WRITER programs, they both write to the same pipe okay.

question from:https://stackoverflow.com/questions/1634580/named-pipes-fifos-on-unix-with-multiple-readers

Answer 1

The O in FIF(O)

means "out". Once your data is "out", it's gone. :-) So naturally if another process comes along and someone else has already issued a read, the data isn't going to be there twice. To accomplish what you suggest you should look into Unix domain sockets. Manpage here. You can write a server which can write to client processes, binding to a filesystem path. See also socket(), bind(), listen(), accept(), connect(), all of which you'll want to use with PF_UNIX, AF_UNIX, and struct sockaddr_un.