20 Apr
2017
20 Apr
'17
3:02 a.m.
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 at least..
#! 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, service.c),
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, also ~81.
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.
Sven
--
https://www.in-ulm.de/~mascheck/bourne/
https://www.in-ulm.de/~mascheck/various/shebang/