[TUHS] Pipes in the Third Edition Unix

Warren Toomey wkt at tuhs.org
Wed Jan 4 07:53:10 AEST 2017

On Tue, Jan 03, 2017 at 10:54:57PM +0200, Diomidis Spinellis wrote:
> Peter Salus writes "The other innovation present in the Third Edition was
> the pipe" ("A Quarter Century of Unix", p. 50).  Yet, in the corresponding
> sys/ken/sysent.c, the pipe system call seems to be a stump.

The Third edition was still written in assembly code. The Fourth edition
was the first to be rewritten in C. So there was a time when both
existed in parallel.
>         1, &fpe,                        /* 40 = fpe */
>         0, &dup,                        /* 41 = dup */
>         0, &nosys,                      /* 42 = pipe */
>         1, &times,                      /* 43 = times */

This code, from the nsys kernel, clearly shows this. The kernel was
being rewritten in C. The C version had not yet caught up with the
functionality in the assembly version of the kernel, which did have pipes.

Cheers, Warren

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