Larry wrote in separate emails I began to write the following spec without knowing that Linux had appropriated the name "splice" for a capability that was in DTSS over 40 years ago under a more accurate name, "copy". The spec below isn't hard: just hook two buffer chains together and twiddle a couple of file desciptors. For stdio, of course, one would need fsplice(3), which must flush the in-process buffers--penance for stdio's original sin of said buffering. Incidentally, the question is not abstract. I have code that takes quadratic time because it grows a pipeline of length proportional to the input, though only a bounded number of the processes are usefully active at any one time; the rest are cats. Splicing out the cats would make it linear. Linear approaches that don't need splice are not nearly as clean. Doug SPLICE(2) SYNOPSIS int splice(int fd0, int fd1); DESCRIPTION Splice connects the source for a reading file descriptor fd0 directly to the destination for a writing file descriptor fd1 and closes both fd0 and fd1. Either the source or the destination must be another process (via a pipe). Data buffered for fd0 at the time of splicing follows such data for fd1. If both source and destination are processes, they become connected by a pipe. If the source (destination) is a process, the file descriptor in that process becomes write-only (read-only). If file descriptor fd0 is associated with a pipe and fd1 is not, then fd1 is updated to reflect the effect of buffered data for fd0, and the pipe's other descriptor is replaced with a duplicate of fd1. The same statement holds when "fd0" is exchanged with "fd1" and "write" is exchanged with "read". Splice's effect on any file descriptor propagates to shared file descriptors in all processes. NOTES One file must be a pipe lest the spliced data stream have no controlling process. It might seem that a socket would suffice, ceding control to a remote system; but that would allow the uncontrolled connection file-socket-socket-file. The provision about a file descriptor becoming either write-only or read-only sidesteps complications due to read-write file descriptors.