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

[Eric Blake <eblake at redhat dot com>]

On 01/28/2016 11:42 AM, Ken Brown wrote:
> On 1/28/2016 12:33 PM, Jon Turney wrote:
>> Future work: I can't see any reason why this script now needs an
>> independent existence, so it could be absorbed by the info package.
> 
> That's fine with me.  There will be a new version of texinfo soon (it's
> currently in pretest), so we can make the transition then.  But I need
> to understand the script before I take it over, and I'm confused by the
> command
> 
>   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
(something like:

install-info foo /usr/share/info/dir || \
  install-info --entry="* $f (foo): $f" $f /usr/share/info/dir

but I don't have the full context for where $f is being defined for why
it is sometimes expanded in make and others by the shell.

> 
> 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.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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