C++ compiler is pretty big and slow tool and if one needs to make full rebuilds very often waiting for build finish is very frustrating. For those guys "ccache" tool was created.
How is it working? Compiler output (*.o files) are cached under key that is computed from preprocessed source code, compiler versions, build switches. This way builds might be much faster.
Qmake is a Makefile generator that comes with QT and allows for easy build of QT-based (and other) projects. In order to join ccache and qmake one have to update so called "mkspecs" files. How to do that?
It's easy using sed (I'm including only sh4 and mipsel crosscompiler toolchains):
# sed -i '/QMAKE_CXX .*= *[^c][^c]/s/= /= ccache /' \ `find /usr/local -name qmake.conf | grep 'linux-\(sh4\|mipsel\)'`
And how to revert:
# sed -i '/ccache/s/ccache / /' \ `find /usr/local -name qmake.conf | grep 'linux-\(sh4\|mipsel\)'`
Of course you can manually launch an editor and update those files, but a bit of sed scripting is many times faster ;-)