How to make C program block until FIFO pipe is empty?

Question

I'm doing IPC using named (FIFO) pipes and I would like to coordinate that program can only write into the pipe when program reading the pipe has read the previously written data out from the pipe. So I would like to block the write until the the pipe is empty. Is this possible?

One option that I though is that write function blocks when the pipe is full. But I would like to do this to much smaller amounts of data than the pipe size in Linux. E.g I would like that program can only write 20 bytes and then it waits until other end has read the data. I think you can not shrink named pipes to be so small. (Minimum size seems to be page file size (4096 bytes)?)

Thanks!

Answer 1

A possible solution is to have the reading process sending a signal to the writing process when it has read some data. You can do this using kill() to send SIGTERM to the writer, since SIGTERM can be catched and handled.