From: utzoo!decvax!microsof!hanss
Newsgroups: net.unix-wizards
Title: . files, defaults, and generality
Article-I.D.: microsof.2558
Posted: Fri Oct 29 01:31:37 1982
Received: Fri Oct 29 06:26:15 1982

Thanks to all those that have told me about the 4.1 function.  for those
that like me, didn't know what I'm talking about, the csh accepts as a first
line a command which will be taken as the 'real' command to run the shell
with.  3.0 bourne does not support this, although 4.1 BSD bourne does. Does
anyone know if 4.0 or 5.0 picked this up?
Thus:

#! /bin/csh -f

will force whatever shell is running to pretend its command was really
whatever was to the right of the first space, and actually run /bin/csh
with a -f flag (even though it was started as /bin/sh...)  Unfortunately
this is documented only by a one line comment at the back of the csh
manual but not documented for the 4.1 bourne shell at all.  This comment does
not mention that it will actually cause the shell to exec a new shell,
nor does it accurately describe the syntax.  Interestingly, it does describe
the syntax I proposed last night.  Obviously, since there was a precedent
and the syntax is only a little stupid (what is the '!' for?) I now modify
my proposal to follow that of BerkElEy.  I also suggest that Berkeley had
better get their documentation act cleaned up.  The army is one of those
organizations you don't want to have mad at you.  They don't flame in the
usenet.  They flame with flamethrowers and tanks and such...

In response to the lone remark that answered the point of my article,
which was about csh -f, (fast...don't read .cshrc):
Yes, combined with the above function, you can achieve the right thing, 
but you will only put the '#! /bin/csh -f' in after you get burned a few
times.  Since the reason people get burned by this sort of thing is because
they don't know what they're doing, don't you think we would all be better
off if the simple, consistent, efficient, safe version were the default,
and allow you to override at your hearts content?  Overriding the default
is invariably easyer than putting it back (set nonoclobber? really, bill!).
And most of the tools have facility for doing it already.  Both major shells
have a 'source' or '.' command, and most other tools, such as macroprocessors
and editors have them too.  Since you have the mechanism to do the thing
efficiently and easily, why complicate matters by adding some new function,
and then making people that want to do things right go out of their way to
turn it off when it causes them grief?  Elsewhere we call this hiding a bug
by introducing another bug, or treating the symptom, not the disease.

				Not afraid to ignoreeof
				-Hans
				decvax!microsoft!hanss