Re: Postpone the evaluation of macro to installation

[Liguo Song <liguo song vanderbilt edu>]

On Tue, 4 Nov 2003, Liguo Song wrote:

> Hi, folks,
> 
> I am trying to build a package for a ruby wrapper. The files will be installed 
> to directories depend on the version of the ruby package and the current host 
> OS, which is the way ruby wants. For example, directory would be 
> /usr/lib/ruby/1.8/i686-linux-gnu/ for ruby-1.8 on RH8.0 and i686, but it will be 
> /usr/lib/ruby/1.6/i386-linux/ for ruby-1.6 on RH7.0 and i386.
> 
> I figure out the way to determine these directories by invoking ruby and defined 
> the results as macros. But all these macros are evaluated at the compile time. 
> So, the directories will not work if the ruby versions are different on the 
> building host and the installing host.
> 
> I can put my files into a directory independent of the ruby version, and put 
> links to them from the right places in the post install phase. But, the macros 
> are all evaluated when I compile the src package, so the direcotries won't work 
> for the installing host.
> 
> My question is whether there is a way to postpone the evaluation of the macros 
> to the installation time? If so, how to achieve this?
> 
> Thanks in advance for any input.
> 
> 
> Liguo (Leo)
> 
> 
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It is a bad habit to reply to oneself. But since no one answered me,
I'd like to share what I found with experiments.

The shell script will be evaluated at the specified phase, such as
%prep, %install, %post, %postun, etc. So, the solution is either
define a shell env variable by `cmd` or just put the `cmd` in the part
you need it.

Hope someone else can share some more elegant solutions.

Thanks.


Liguo (Leo)