Re: [TUHS] First appearance of named pipes

On 3/10/20 1:29 AM, arnold(a)skeeve.com wrote: Thank you for your reply Arnold. As I was reading your reply, I realized that I did not fully convey the question that I was still mulling over in my head. (More in a moment.) This thread is one of about three things happening in my life that have to do with pipes, FIFOs, and file descriptors. I managed to articulate the simpler of the questions while reading Noel's email. The larger more onerous question is could I leverage exec to alter where file descriptors 0 (STDIN), 1 (STDOUT), and 2 (STDERR) are set to, including changing 1 to the value of a FIFO, and 0 of a subsequent command to also be the value of the FIFO, thus have pipe like behavior between two commands without using a pipe or redirection as in ">". This has also gotten me to wonder about the possibility of having multiple commands output to a file descriptor; 1 / 2 / other, that is input to a separate command. Sort of the opposite of tee, in a manner of speaking. I'll try to articulate: $ mkfifo test.fifo $ exec 3>&1 $ exec 1> test.fifo $ for l in {a..z}; do echo $l; sleep 1; done & $ for L in {A..Z}; do echo $L; sleep 1; done & $ for n in {1..100}; do echo $n; sleep 1; done & $ exec 1>&3 $ cat test.fifo This seems special to me in that I have three processes (for loops) writing into what is effectively the same pipe. After having mulled this over for a few days and typing this out, I realize that the "pipe" is really just a fifo and that in this case the fifo is a named pipe on the file system. I could do the same thing with a file. Historically I would have done the same thing with a file. But now I realize that the file is not required and that I can use a fifo which is in memory and never hits the disk. (Save for creating the name interface to the pipe / fifo.) At least, I think that's all accurate. I would be very eager to learn from anyone who is willing to teach me pointers. :-) -- Grant. . . . unix || die