bash: This command enters a sub-shell to isolate environment changes. export QTDIR=$PWD: This command defines where the root of the Qt directory is located. export LD_LIBRARY_PATH=$QTDIR/lib: This command sets up the location of libraries for the build process. export PATH=$QTDIR/bin:$PATH: This command allows the build process to find supporting executables. -prefix /opt/qt-&qt-version;: This command sets up the install destination. -qt-gif: This command adds support for gif files to the libraries. -system-libpng -system-libmng -system-zlib -system-libjpeg: This command forces the library to use the shared libraries that are on your system instead of recreating its own set of support libraries for these functions. -no-g++-exceptions: This command disables the exceptions coding generated by the C++ compiler. -thread: This command compiles the library to support multi-threading. ln -sfn qt-&qt-version; /opt/qt: This command standardizes the location of the Qt libraries to the ld.so.conf entry described below. ln -s libqt-mt.so /opt/qt/lib/libqt.so: This command allows configure scripts to find a working Qt installation. cp -r doc/man /opt/qt/doc: This command installs the man directory which is missed by make install. cp -r examples /opt/qt/doc: This command installs the examples directory which is missed by make install. exit: This command returns to the parent shell and eliminates envirnment variables set earlier.