在Linux中在运行时重定向FIFO

Question

I am trying to implement a runtime reconfigurable IPC in C++ under Linux using POSIX IPC. In the current configuration I have a process A communicating through a FIFO with a process B. The process B takes the data from the FIFO, make some modifications and sends them to another process C through another FIFO. Here's a graphical representation:

Then, at run-time I would like to kill the process B, and be able to allow process A to send the data through the FIFO between B and C:

How can I do that?

Answer 1

If you kill a process, its open filedescriptors are all closed. So if you kill B, this will cause an EOF on the FIFO as seen by C. However, if you have a named FIFO that persists after B is closed, C can continue to read from the filedescriptor associated with the FIFO, although it will return EOF immediately continuously until the other end is reopened.

Another option is to have B send its output back to A, which then forwards that output to C. This way, it will always control what gets sent to C, and C does not have to worry about its FIFO being closed and reopened.