On Tue, Feb 12, 2013 at 04:22:08PM -0500, Matei David wrote: > Generally speaking, it took me quite some time to figure out how to > properly create a "double pipe" without using any intermediate files or > fifos. The concept is very easy: in -> tee -> two parallel, independent > pipes -> join -> out. A first complication is the limited pipe capacity, > and the possibility of one side getting stuck if the other stops pulling in > data. I then wrote a cat-like program which doesn't block on stdout, but > keeps reading stdin, buffering in as much data as needed. I used it at the > very end of either pipe. But then I had to create the actual processes, and > then I stumbled upon all these issues with coproc and file descriptors. You > leave the wrong one open and the thing gets stuck... I wish there was a > howto on this subject.
I really like to see these threads that poke at the edges of things in bash, providing a great learning opportunity for lurkers like me. But that said, perhaps what you're trying to so might be handled easily by socat; from http://www.dest-unreach.org/socat/doc/README: socat is a relay for bidirectional data transfer between two independent data channels. Each of these data channels may be a file, pipe, device..., a socket..., a file descriptor (stdin etc.) ... Just a thought. Ken
