Install gcc 9 on Ubuntu LTS 12.04,14.04,16.04 and 18.04

install-gcc-9.sh

#!/usr/bin/env sh

sudo apt-get update -y && \
sudo apt-get upgrade -y && \
sudo apt-get dist-upgrade -y && \
sudo apt-get install build-essential software-properties-common -y && \
sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y && \
sudo apt-get update -y && \
sudo apt-get install gcc-9 g++-9 -y && \
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 60 --slave /usr/bin/g++ g++ /usr/bin/g++-9 && \
sudo update-alternatives --config gcc

select gcc-9

国内访问这个源太慢了，需要替换一下

# 备份
sudo cp /etc/apt/sources.list.d/ubuntu-toolchain-r-ubuntu-test-bionic.list /etc/apt/sources.list.d/ubuntu-toolchain-r-ubuntu-test-bionic.list.zjr

# 修改
cat /etc/apt/sources.list.d/ubuntu-toolchain-r-ubuntu-test-bionic.list
#deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu bionic main
# deb-src http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu bionic main
deb https://launchpad.proxy.ustclug.org/ubuntu-toolchain-r/test/ubuntu bionic main
# deb-src https://launchpad.proxy.ustclug.org/ubuntu-toolchain-r/test/ubuntu bionic main