I feel like there should be a simple way of doing this, but my googlefu is failing so I'd really appreciate some info on how to switch (or even permanently change) which version of Qt is used when doing qmake.  If I ask which version I get the following:~ $ qmake --versionQMake version 3.0Using Qt version 5.0.1 in /usr/lib/x86_64-linux-gnuI've install QtCreator, but I'm not sure where to go from here.
How do I change which version of Qt is used for qmake?
make;qt;qtcreator
This isn't necessarily Unix/Linux specific, so you are probably better asking this on Stack Overflow. Never the less, QtCreator is usually quite good at detecting alternative Qt installs, just create a new project and look under the Projects tab on the left. You can set different build configurations there. There should be a drop down box to select from the various installed versions for each configuration.Otherwise, it seems to the QTDIR environmental variable is used to set the Qt version. By default QtCreator sets this to /usr/share/qt4 for me, so setting it to the equivalent path (ie the one where the configuration files are) should make qmake build with a different version. You could test with something like:QTDIR=/usr/share/qtX qmake --versionIt may also be possible to set this in the .pro file, but if so it is undocumented (as with quite a lot of qmake variables).Also, if you want to build with a specific major version, qmake is usually just symlinked to a binary for the default major version. The real binaries are qmake-qt4, qmake-qt5 etc. Also see man qtchooser and the qtX-default packages on Debian based systems.UpdateThere is a bug with qtchooser on Ubuntu 13.04 and 13.10 which seem to affect the way Qt applications detect different Qt versions, see https://bugs.launchpad.net/ubuntu/+source/qt4-x11/+bug/1177823. This may affect QtCreator also.