cvs commit: doc/en_US.ISO8859-1/articles/rc-scripting article.sgml

[Yar Tikhiy]

On Sun, Mar 04, 2007 at 02:52:49PM -0800, Doug Barton wrote:
> Yar Tikhiy wrote:
> >On Sat, Mar 03, 2007 at 10:35:27PM -0800, Doug Barton wrote:
> >>Yar Tikhiy wrote:
> >>>yar         2007-03-03 10:11:34 UTC
> >>>
> >>> FreeBSD doc repository
> >>>
> >>> Modified files:
> >>>   en_US.ISO8859-1/articles/rc-scripting article.sgml 
> >>> Log:
> >>> Explain how an rc.d script can use extra command-line arguments.
> >>> 
> >>> Revision  Changes    Path
> >>> 1.9       +138 -0    
> >>> doc/en_US.ISO8859-1/articles/rc-scripting/article.sgml
> >>>
> >>>http://www.FreeBSD.org/cgi/cvsweb.cgi/doc/en_US.ISO8859-1/articles/rc-scripting/article.sgml.diff?&r1=1.8&r2=1.9&f=h
> >>Yar,
> >>
> >>This good stuff, thanks! I have one quibble with the last paragraph. 
> >>The shift in rc.subr isn't "apparent" as you phrase it, it's literal:
> >
> >Yeah, I tried to hide a thing from the reader which he should already
> >have known: the shift command. :-)
> 
> Again, looking at it from the point of view of a naive reader, there 
> is a difference between "I know that the shift command exists, and 
> sort of know what it does" and "I know how the shift command is used 
> by rc.subr to affect the command line arguments to my script." Your 
> article is (to some extent) about teaching the latter, so I think it's 
> reasonable to spend some time spoon feeding the reader until they are 
> ready for some meat.

Agreed!  The new revision tries to do that better.

> >>run_rc_command()
> >>{
> >>    ...
> >>    # Don't repeat the first argument when passing additional command-
> >>    # line arguments to the command subroutines.
> >>    #
> >>    shift 1
> >>    rc_extra_args="$*"
> >
> >Oh my...  Now I see why existing rc.d scripts use this bogus command:
> >
> >	run_rc_command "$*"
> >
> >It's because rc.subr will mess up the arguments anyway.
> 
> I think it's more likely that someone would use $* vs. $@ out of force 
> of habit. :)

It's a bad habit IMHO unless one really means $* :-)

> >Perhaps
> >we should investigate if "$@" can be used consistently to preserve
> >original boundaries between arguments to an rc.d script...
> 
> I wouldn't object to some testing on that. I'll change my local copy 
> and see how it behaves.

I took a look at that and found that, as long as we support for
random shell expressions in $foo_cmd, the magic wand of "$@" cannot
help us without some additional black magic.  If $foo_cmd were
guaranteed to be merely the name of a function or simple command,
then we would need no final eval to execute $foo_cmd.  But stuffing
shell expressions in $foo_cmd is neat and should be supported.
Perhaps we should just tell people that they cannot pass hairy
arguments to rc.d scripts -- each argument must be a simple word.

-- 
Yar