Скачать или смотреть Upgrade gcc and g++ in Ubuntu

A brief description of how to upgrade gcc and g++ from version 5.4.0 to version 6.2.0 in Ubuntu Linux. Please click the "Show more" (if the Update November 2019 is not displayed) text below for the updated commands for gcc-9 an g++-9.

November 2019:
After a question from Gery M:
To get gcc 9.x and g++ 9.x, just follow the steps described, replacing the version number with 9.
If you are starting from gcc 8.x or lower you may have to do a stepped upgrade. For example, to go from gcc-5 to gcc-6 (g++-5 to g++-6). Follow the steps outlined below and in the video, but replace the version number with the version immediately following the installed version:
(installed) gcc-5 g++-5 (upgrade to)
(installed) gcc-6 g++-6 (upgrade to)
(installed) gcc-7 g++-7 (upgrade to)
(installed) gcc-8 g++-8 (upgrade to)
gcc-9 g++-9

Keep a good eye on any error messages. If necessary, you will have to upgrade any seemingly unrelated files to a more current version. This will ensure your compiler upgrade works properly and you will, hopefully, not run into obscure and difficult, if not impossible, to fix errors in your application/library compilations.
Usual caveats apply

April 2019:
To get gcc-8 and g++-8, as before replace gcc-6 or gcc-7 with gcc-8 and g++-6 or g++-7 with g++8.
The command sequence will now be:
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-8 g++-8
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 20 --slave /usr/bin/g++ g++ /usr/bin/g++-8

Sept 2017
This works with upgrading gcc-6/g++-7 as well. If you are starting from a version of gcc that is lower than 6, it is probably better to to do incremental upgrades rather than a straight up upgrade.
Just replace the gcc-6 and g++-6 with gcc-7 and g++-7
Usual caveats apply.

List of Commands:
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-6 g++-6
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 20 --slave /usr/bin/g++ g++ /usr/bin/g++-6
(corrected after comment from Belmokaddem Adil - thank you! :D )

I have also done a quick blog post at: http://ovenproof-linux.blogspot.com/2...