Ubuntu under GCC, g++ and Gfortran version switching

First step: Using which gcc, which g++, and which gfortran to view the location, my display results are:/usr/bin/gcc;/usr/bin/g++ and/usr/bin/gfortran

Part Two: First, take a look at what version of GCC you have installed in your Ubuntu command: ls/usr/bin/gcc*-L;

The gcc/g++ in Ubuntu 12.04 are all 4.6, and we downgrade the system to 4.4 by default.

$sudo Apt-get Install gcc-4.4

$sudo update-alternatives--INSTALL/USR/BIN/GCC gcc/usr/bin/gcc-4.4 40

(Here "40" is the priority, the higher the value the higher the priority)

$sudo update-alternatives--INSTALL/USR/BIN/GCC gcc/usr/bin/gcc-4.6 60

(This machine comes with a setting of 60 higher priority)

Select the system default GCC

$sudo update-alternatives--config gcc

Selection Path Priority Status

------------------------------------------------------------

* 0/usr/bin/gcc-4.6 Auto mode

1/usr/bin/gcc-4.4 Manual Mode

2/usr/bin/gcc-4.6 Manual Mode

The default system with the highest priority,

We're going to choose 1 here.

Next, g++ the same steps

$sudo Apt-get Install g++-4.4

$sudo Apt-get Install G++-4.4-multilib

$sudo update-alternatives--install/usr/bin/g++ g++/usr/bin/g++-4.4 40

$sudo update-alternatives--install/usr/bin/g++ g++/usr/bin/g++-4.6 60

$sudo update-alternatives--config g++

Selection Path Priority Status

------------------------------------------------------------

* 0/usr/bin/g++-4.6 Auto mode

1/usr/bin/g++-4.4 Manual Mode

2/usr/bin/g++-4.6 Manual Mode

Select 1.

If you want to change to a higher version of the ready

Update-alternatives--config command Switch!

Ubuntu under GCC, g++ and Gfortran version switching