Quick sed question

Dan Nicholson dbn.lists at gmail.com
Wed Dec 3 00:19:52 UTC 2008


2008/12/2 Paul <paul at 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.

--
Dan




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