script to swap gcc compiler in ubuntu

gcc_compiler_swap.bash

# Tested in Ubuntu 14.04 
# 14.04 comes with gcc version 4.8.4

# Reference: http://lektiondestages.blogspot.in/2013/05/installing-and-switching-gccg-versions.html

sudo add-apt-repository ppa:ubuntu-toolchain-r/test 
sudo apt-get update
sudo apt-get install gcc-4.9
sudo apt-get install g++-4.9


sudo update-alternatives --remove-all gcc 
sudo update-alternatives --remove-all g++

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 10 --slave /usr/bin/g++ g++ /usr/bin/g++-4.8
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 20 --slave /usr/bin/g++ g++ /usr/bin/g++-4.9

sudo update-alternatives --config gcc

# or 

######################## gcc_set_default_version.bash: start #################################

#!/bin/bash 
usage() {
        echo 
        echo Sets the default version of gcc, g++, etc
        echo Usage:
        echo 
        echo "    gcc-set-default-version <VERSION>"
        echo 
        exit
}
cd /usr/bin
if [ -z $1 ] ; then 
        usage;
fi 
set_default() {
        if [ -e "$1-$2" ] ; then 
                echo $1-$2 is now the default
                ln -sf $1-$2 $1
        else 
                echo $1-$2 is not installed
        fi
}
for i in gcc cpp g++ gcov gccbug ; do 
        set_default $i $1
done

########################### gcc_set_default_version.bash: end ################################

# save the above script as gcc_set_default_version.bash and chmod 755 to the script.

sudo sh gcc_set_default_version.bash 4.9  #any version you have in update-alternatives.