查看系统已安装的 GCC 版本

ls -l /usr/bin/gcc*

root@c98c1b416c01:/home# ls -l /usr/bin/gcc*
lrwxrwxrwx 1 root root     21 Jan 16 22:09 /usr/bin/gcc -> /etc/alternatives/gcc
-rwxr-xr-x 1 root root 255080 Mar 20  2014 /usr/bin/gcc-4.4
-rwxr-xr-x 1 root root 915736 Oct  4 19:23 /usr/bin/gcc-5
lrwxrwxrwx 1 root root      8 Feb 11  2016 /usr/bin/gcc-ar -> gcc-ar-5
-rwxr-xr-x 1 root root  31136 Oct  4 19:23 /usr/bin/gcc-ar-5
lrwxrwxrwx 1 root root      8 Feb 11  2016 /usr/bin/gcc-nm -> gcc-nm-5
-rwxr-xr-x 1 root root  31136 Oct  4 19:23 /usr/bin/gcc-nm-5
lrwxrwxrwx 1 root root     12 Feb 11  2016 /usr/bin/gcc-ranlib -> gcc-ranlib-5
-rwxr-xr-x 1 root root  31136 Oct  4 19:23 /usr/bin/gcc-ranlib-5
-rwxr-xr-x 1 root root   2189 Dec  3  2015 /usr/bin/gccmakedep

设置 GCC 各版本优先级

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 60
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 50

设置 G++ 各版本优先级

sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 60
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-5 50

版本号 gcc-5、gcc-4.4、g++-5 、g++-4.4 以及 优先级数值 40、50 可以根据自己需要更改。优先级数值范围为0到100。设置好 GCC、G++ 各版本优先级后可进行优先级查看，以及个版本切换。

GCC 各版本切换

sudo update-alternatives --config gcc

root@c98c1b416c01:/home# update-alternatives --config gcc
There are 2 choices for the alternative gcc (providing /usr/bin/gcc).

  Selection    Path              Priority   Status
------------------------------------------------------------
* 0            /usr/bin/gcc-4.4   60        auto mode
  1            /usr/bin/gcc-4.4   60        manual mode
  2            /usr/bin/gcc-5     50        manual mode

Press <enter> to keep the current choice[*], or type selection number: 

G++ 各版本切换

sudo update-alternatives --config g++

root@c98c1b416c01:/home# update-alternatives --config g++
There are 2 choices for the alternative g++ (providing /usr/bin/g++).

  Selection    Path              Priority   Status
------------------------------------------------------------
* 0            /usr/bin/g++-4.4   60        auto mode
  1            /usr/bin/g++-4.4   60        manual mode
  2            /usr/bin/g++-5     50        manual mode

Press <enter> to keep the current choice[*], or type selection number: 

另一种切换方法

在 ~/.bashrc 文件中增添加

alias gcc='/usr/bin/gcc-4.4'
alias g++='/usr/bin/g++-4.4'

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