Re: [PATCH setup 0/3] Setup replacement for incver_ifdep

[Jon Turney <jon dot turney at dronecode dot org dot uk>]

On 28/01/2016 20:22, Eric Blake wrote:
> On 01/28/2016 01:17 PM, Ken Brown wrote:
> > > >     install-info $f /usr/share/info/dir ||
> > > >     install-info --entry="* $$f ($f): $$f" $$f /usr/share/info/dir
> > > >
> > > > First, what do those double dollar signs mean?
> > >
> > > If this is from a Makefile snippet, it says that $f is a make variable,
> > > while $$ turns into a literal $f for the shell that make invokes
> >
> > It's not a Makefile snippet; it's a snippet from a bash shell script.  Here's more context:
> >
> >    for f in /usr/share/info/*; do
> >        case "$f" in
> >            *\**)
> >                ;;
> >            */dir|*/dir.info*)
> >                ;;
> >            *-[0123456789]*)
> >                ;;
> >            *)
> >                install-info $f /usr/share/info/dir ||
> >                install-info --entry="* $$f ($f): $$f" $$f /usr/share/info/dir
> >                ;;
> >        esac
> >    done
> >
> > It looks to me like all those double dollar signs will just get expanded to the PID of the bash process, so that the second install-info command is nonsense.  But maybe I'm missing something.
>
> Oooh, scary. Yeah, it looks like utter nonsense, as that would indeed
> give the PID of bash followed by a literal f, but who wants to look up
> info of '1234f'?  I wonder if someone writing the script copied
> incorrectly from a Makefile?

Crazy.  I didn't add this part, so I guess it's been there for a long time.

> > Second, why is the second line needed, i.e., under what circumstances
> > would it be expected to succeed after the first install-info command
> > failed?
>
> Sadly, I don't know install-info enough to answer that one.

I think the first install-info command would fail if the .info file is 
missing a START-INFO-DIR-ENTRY/END-INFO-DIR-ENTRY block, in which case 
install-info should fail with a 'install-info: warning: no info dir 
entry in `xxx.info''

Since such a .info file is apparently valid (although I don't think we 
have any instances of such), I guess the nonsense after the || should be 
fixed to use '$f' correctly.