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Re: effective difference between "Requires:" and "PreReq:"?



On Sat, Dec 27, 2003 at 03:31:21PM -0500, Robert P. J. Day wrote:
>   i just want to clarify the difference between the "Requires" and "PreReq"
> directives in a spec file.
> 
>   from johnson's book, i read that "In most usage, a PreReq: acts just like
> a Requires:...".  the stated difference is that PreReq: exists only to allow
> for a manual order to dependencies.  but what is the technical difference?
> 
>   in both cases, if a listed dependency is already on the system, then you're
> good to go, so there's no difference there.  so the only difference could be
> if you're trying to install two packages with some kind of dependency 
> relationship, in the same command.
> 
>   imagine package A, which has a PreReq: or Requires: directive listing 
> package B, neither of which is on the host at the moment.  is it legal in
> either case to do 
> 
>   # rpm -i A.rpm B.rpm
> 
> if A "Requires" B, is the above legal?  and does this differ if A lists B as
> a PreReq?  and, in either case, if the operation is legal, is B forced to be
> installed first?  or only in the case of B being a PreReq?  or is it arbitrary?
> 

The only difference between PreReq: and Requires: has to do with
dependency loops (which should not happen anyways).

If a loop is encountered, all Requires: in the loop will be ignored, PreReq:'s
will be honored.

Theere are other means to snip loops more precisely.

73 de Jeff

-- 
Jeff Johnson	ARS N3NPQ
jbj@redhat.com (jbj@jbj.org)
Chapel Hill, NC




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