# 如将gcc-4.8切换为gcc-5
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-5 g++-5
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 60 --slave /usr/bin/g++ g++ /usr/bin/g++-5
切换回去
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 80 --slave /usr/bin/g++ g++ /usr/bin/g++-4.8
http://www.cnblogs.com/panfeng412/archive/2011/10/20/library_path-and-ld_library_path.html