14 Jul
2016
14 Jul
'16
7:18 p.m.
I remember hearing that originally the Unix shell had control structures
(e.g. if, while, case) implemented through external commands. However,
I can't see this reflected in the source code. The 7th Edition Bourne
shell has these commands built-in (usr/src/cmd/sh/cmd.c), while the 6th
Edition (usr/source/s2/sh.c) seems to lack them completely.
The only external command I found was glob, which performed wildcard
expansion.
Am I missing something? Was this implemented in a version that was
never released? If so, does anyone know how this implementation worked?
(Nested commands might require holding some sort of globally
accessible stack.)