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Re: Quick sed question



Dan Nicholson wrote:
> 2008/12/2 Paul <paul all-the-johnsons co uk>:
>> Hi,
>>
>> I'm about to rebuild mono-2.x with Mike's patch for libgdiplus but would
>> like to know what the following sed line means (it's caused a problem
>> with building for x86_64 mono)
>>
>> 's,@''bindir@,$(bindir),g'
>>
>> what does the ,g do?
> 
> The g mean, keep finding every match on a given line. Otherwise, you
> just get the first match, which may be what you want.
> 
>> The reason I'm asking is that in order to get things to build with mono
>> easier (and causing fewer upgrade hassles in trying to find *every* use
>> of /usr/lib rather than %{_libdir}), I've started to use a find-all sed
>> script. Unfortunately, on x86_64, this is giving me /usr/lib6464 and I'm
>> wondering if the ,g has anything to do with the replication of the the
>> 64 (I doubt it has).
>>
>> The script works fine in other mono-based applications, so I'm trying to
>> find why mono would act in such a way.
>>
>> The script is as follows
>>
>> find . -name Makefile.in -or -name Makefile.am -or -name \*.pc.in \
>>       -or -name \*.in -or -name \*.make \
>>       | while read f ;
>>         do
>>           sed -i -e 's!$(prefix)/lib!%{_libdir}!' "$f"
>>           sed -i -e 's! prefix@/lib!%{_libdir}!' "$f"
>>           sed -i -e 's!/usr/lib!%{_libdir}!' "$f"
>>           sed -i -e 's!${prefix}/lib!%{_libdir}!' "$f"
>>           sed -i -e 's!${exec_prefix}/lib!%{_libdir}!' "$f"
>>           sed -i -e 's!${prefix}/@reloc_libdir !%{_libdir}!' "$f";
>>         done
> 
> Maybe the g is causing the problem, but you'd have to see more context
> to know. Two suggestions:
> 
> 1. sed takes multiple -e patterns, so you don't need to fork it 6
> times per file.
> 
> 2. Giving an argument to -i (on sed > 4.1.2 I think) will make a
> backup with the argument as suffix. E.g., `sed -i.bak s/foo/bar/ file'
> will give you file and the original file.bak. Then you can diff them
> to see what you just did.
> 
You're substituting some lines multiple times with the given sequence of
substitutions.  For instance:

start with:
  LIBDIR= prefix@/lib
This line runs:
  sed -i -e 's! prefix@/lib!%{_libdir}!' "$f"
And you have:
  LIBDIR=/usr/lib64
Then this line runs:
  sed -i -e 's!/usr/lib!%{_libdir}!' "$f"
And you have:
  LIBDIR=/usr/lib6464

Ignacio's message has a solution for this since it checks that the "lib"
pattern doesn't have a "6" after it.

-Toshio

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