问题
I have both qt4 and qt5 on my Linux system. qt4 is used by default. What is a clean way to change that so that qmake uses qmake-qt5 by default?
回答1:
The system might have different meta packages that handle the default.
For example on Debian there is a qt4-default and a qt5-default package, installing one of them will uninstall the other and set the symlinks appropriately
回答2:
There is a tool named qtchooser to switch between Qt versions. On Debian and Ubuntu you can install it with apt-get install qtchooser.
Easiest way is to use it to list the alternatives and then create QT_SELECT environment variable.
$ qtchooser -list-versions
4
5
default
opt-qt55
qt4-i386-linux-gnu
qt4
qt5-i386-linux-gnu
qt5
Then you create QT_SELECT environment variable and set e.g. export QT_SELECT=4 or export QT_SELECT=5.
回答3:
Step 0: Install qtchooser in your system.
$sudo apt-get install qtchooser
Step 1: locate your qtchooser configure file in your system.
$ locate qtchooser | grep conf
/usr/lib/x86_64-linux-gnu/qt-default/qtchooser/default.conf
/usr/lib/x86_64-linux-gnu/qtchooser/4.conf
/usr/lib/x86_64-linux-gnu/qtchooser/5.conf
/usr/lib/x86_64-linux-gnu/qtchooser/qt4.conf
/usr/lib/x86_64-linux-gnu/qtchooser/qt5.conf
The command result may be different from yours. Those x.conf files represent all of qt versions qtchooser could recognized in your system. Each x.conf file is a symbolic link to a file configured the qt you have installed. Modifying the default.conf could configure the default qt version you expected.
Step 2: Find out the file location the symbolic link file default.conf linked to.
$ls -l /usr/lib/x86_64-linux-gnu/qt-default/qtchooser/default.conf
lrwxrwxrwx 1 root root 53 x xx xxx /usr/lib/x86_64-linux-gnu/qt-default/qtchooser/default.conf -> ../../../share/qtchooser/qt4-x86_64-lnux-gnu.conf
Step 3: Create your qt version conf file
The result of step 2 shows the location of all qt version conf file: /usr/share/qtchooser. You just create a conf file specified your qt version in this path. For example, my qt is installed at /opt/Qt5.13.1/ and I want to set this qt version as the default one in my system. We could create a file named like qt5.13.1.conf.
$cd /usr/share/qtchooser
$sudo vi qt5.13.1.conf
and fill in the following two lines: first line means the qmake location and another represents the library path.
/opt/Qt5.13.1/5.13.1/gcc_64/bin
/opt/Qt5.13.1/5.13.1/gcc_64/lib
Step 4: Set your qt as the default one.
Just modify the default.conf symbolic link to your qt conf file created at step 3.
$cd /usr/lib/x86_64-linux-gnu/qt-default/qtchooser/
$sudo ln -snf ../../../share/qtchooser/qt5.13.1.conf default.conf
After complete those steps, the default qt has been configured and you can type following command to test and it should be your qt as the default.
$qmake -v
来源：https://stackoverflow.com/questions/39735998/make-qmake-use-qt5-by-default