On 07/31/2014 11:23 PM, Bruce Dubbs wrote: > Armin K. wrote: >> On 07/31/2014 11:10 PM, Bruce Dubbs wrote: >>> Armin K. wrote: >>>> The >>>> changes include rewritten Qt4 and Qt5 instructions so they can be once >>>> again installed alongside each other in /usr, using qtchooser to >>>> dynamically switch between two installations. The instructions were >>>> also >>>> simplified so that only one configure line is there and prefix can be >>>> changed before running it. >>> >>> I'm curious. If there are two users on the system and user1 wants to >>> build some packages using qt4 and user2 wants to build using qt5, how is >>> that possible with qtchooser? >>> >>> And yes, I've been in that situation, although it was qt3/qt4 at the >>> time. > >> http://www.linuxfromscratch.org/~krejzi/blfs-systemd/x/qt4.html >> >> See "Dealing with multiple Qt versions". I believe this was the only >> significant improvement over the previous instructions that used >> qtchooser. > > That's not clear to me that it solves the problem. I haven't looked at > qtchooser recently, but I thought it created symbolic links so that it > changed the current default qt version for everyone. That means that > all developers on a system must use the same qt version unless > qtchoosser is run again. > > Please correct me if I don't understand properly. > > -- Bruce >
No. qtchooser is a small utility. The Qt programs such as qmake, moc, uic, etc are symlinks to qtchooser and always in PATH. Depending on the configuration file or environment variable, qtchooser can be made to use Qt executables and libraries from different paths. Configuration file only sets the default, which is always Qt4 in that setup, because most programs that use Qt5 look for executables with -qt5 suffix. There is no good way for me to explain how it does things, but I believe this is the simplest: It does not change symlinks. It is basically a wrapper for Qt executables which can be used to switch between different Qt versions *without* a need to change either symlinks or PATH variable, by merely setting a environment variable for default Qt setup (QT_SELECT=qt4 ; qmake = Qt4 qmake (default), export QT_SELECT=qt5 ; qmake = Qt5 qmake). -- Note: My last name is not Krejzi.
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