[TUHS] Excise process from a pipe

Noel Chiappa jnc at mercury.lcs.mit.edu
Fri Jul 11 01:10:21 AEST 2014

    > From: Larry McVoy <lm at mcvoy.com>

    > Every utility that you put in a pipeline would have to be reworked to
    > pass file descriptors around

Unless the whole operation is supported in the OS directly:

	if ((pipe1 = process1->stdout) == process2->stdin) &&
	   ((pipe2 = process2->stdout) == process3->stdin) {
		prepend_buffer_contents(pipe1, pipe2);
		process1->stdout = process2->stdout;

to be invoked from the chain's parent (e.g. shell).

(The code would probably want to do something with process2's stdin and
stdout, like close them; I wouldn't have the call kill process2 directly, that
could be left to the parent, except in the rare cases where it might have some
use for the spliced-out process.)


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