hi, I have a problem. I've done a lil program which gets from the server the given persons username a personal folder. I made it with a pipe calling popen with a command, but how can i make the same thing using fifo. I make the fifo with mkfifo() func. and than what. How do I tell the sertver using the fifo file that I need a persons usr name and personal folder.
any kind of help is appreciated.

A fifo works pretty much like a pipe.... In both cases one process reads and the other process writes. This brings up the main difference, with modern pipes, it is possible to move data in both directions...but this is seldom done. A fifo is unidirectional only.

For starters, you may find this page useful:

http://beej.us/guide/ipc/fifos.html

Are you sure you need fifo's or is it only a trial ?
instead of fifo's you can easly use (unix-) sockets or do 'man socketpair' if you have to processes to connect.