> The two requests would have been more convincing if they demonstrated
> a definite need.
Another case: "pipe" stderr into a separate pipeline from stdout.
This is useful for stderr as a status channel.
fifo_stderr1=$(mktemp --fifo stderr.XXXXXX)
fifo_stderr2=$(mktemp --fifo stderr.XXXXXX)
listener1 < $fifo_stderr1 &
listener2 < $fifo_stderr2 &
cmd1 2> $fifo_stderr1 | cmd2 2> $fifo_stderr2
Another case: Use file descriptor 3 as a command and control channel.
Output has two default file descriptors (stdout and stderr), why not
input (stdin and cmdin)? This is especially helpful for repairing a
nest of processes that are connected by pipes.
fifo_cmdin1=$(mktemp --fifo cmdin.XXXXXX); sleep 999000 > $fifo_cmdin1 &
fifo_cmdin2=$(mktemp --fifo cmdin.XXXXXX); sleep 999000 > $fifo_cmdin2 &
cmd1 3< $fifo_cmdin1 | cmd2 3< $fifo_cmdin2 &
echo quit > $fifo_cmdin1
--
