Processes hang on read
The call to read() is blocking until more data shows up. From the man page for pipe
If a process attempts to read from an empty pipe, then read(2) will block until data is available. If a process attempts to write to a full pipe (see below), then write(2) blocks until sufficient data has been read from the pipe to allow the write to complete. Nonblocking I/O is possible by using the fcntl(2) F_SETFL operation to enable the O_NONBLOCK open file status flag.
After you open each file descriptor before you enter that while loop do this to each one:
fcntl(fd, F_SETFL, O_NONBLOCK);However, you really should read up on blocking vs. non-blocking I/O, including reading the man pages for pipe, read, fcntl, etc.