[TUHS] Bourne shell and comments
steffen at sdaoden.eu
Thu Apr 20 08:07:28 AEST 2017
Sven Mascheck <mascheck at in-ulm.de> wrote:
|On Wed, Apr 19, 2017 at 06:48:34AM +1000, Warren Toomey wrote:
|> I was trying to configure C news on 2.9BSD today and I found that its
|> Bourne shell doesn't grok # comments. The Bourne shell in 2.11BSD does.
|> So I thought: when did the Bourne (and other) shells first grok # as
|> indicating a comment? Was this in response to #! being added to the
|> kernel, or was it the other way around? And was the choice of #!
|> arbitrary, or was it borrowed from somewhere else?
|> Datum point: 2.9BSD's kernel can recognise #!, but the sh can't recognise \
|Dennis' email about #! to Berkeley is dated Jan 10 '80.
|I've never seen any hint, how the bang in #! was chosen. Looks racy \
|#! on BSDs was available as compile time option in 4.0BSD (~Oct '80?)
|and default on 4.2BSD (~Sep '83).
|BTW, AFAIK, the #! implementation in 2.8BSD (compile time option) is not
|from research but seems to come from U.S. Geological Survey, Menlo Park.
|The BSD csh hack in sh&csh (# special as first character in a file, \
|came with 3BSD, also in '80.
|I found # as comment character in the BSD-sh first in CSRG 4.1.snap
|(~Apr '81, word.c). And at Bell Labs, as mentioned, it came with SysIII, \
|BTW, 4.3BSD ('86), and thus 2.10 BSD, brought an interesting change:
|# is only recognized in non-interactive mode. In interactive mode
|you actually get this:
| $ # echo x
| #: not found
|This was not changed in 4BSD until sh was replaced by ash in 4.3 Net/2.
Hmm. Kurt Shoens added # as a null() saying "The do nothing
command for comments." before that (2BSD, file copyright 1979).
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