To install qt58-qtmacextras, run the following command in macOS terminal (Applications->Utilities->Terminal)
sudo port install qt58-qtmacextras
To see what files were installed by qt58-qtmacextras, run:
port contents qt58-qtmacextras
To later upgrade qt58-qtmacextras, run:
sudo port selfupdate && sudo port upgrade qt58-qtmacextras
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