Смена альтернатив

[det_random]

Например, хочется иметь разные версии g++ на одной тачке. Нет проблем, http://askubuntu.com/questions/26498/choose-gcc-and-g-version:

First erase the current update-alternatives setup for gcc and g++:

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

Install Packages

It seems that both gcc-4.3 and gcc-4.4 are installed after install build-essential. However, we can explicitly install the following packages:

sudo apt-get install gcc-4.3 gcc-4.4 g++-4.3 g++-4.4

Install Alternatives

Symbolic links cc and c++ are installed by default. We will install symbol links for gcc and g++, then link cc and c++ to gcc and g++ respectively.

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.3 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 20

sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.3 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 20

sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc

sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++

Configure Alternatives

The last step is configuring the default commands for gcc, g++. It's easy to switch between 4.3 and 4.4 interactively:

sudo update-alternatives --config gcc
sudo update-alternatives --config g++

Or switch using script:

#!/bin/sh

if [ -z "$1" ]; then
echo "usage: $0 version" 1>&2
exit 1
fi

if [ ! -f "/usr/bin/gcc-$1" ] || [ ! -f "/usr/bin/g++-$1" ]; then
echo "no such version gcc/g++ installed" 1>&2
exit 1
fi

update-alternatives --set gcc "/usr/bin/gcc-$1"
update-alternatives --set g++ "/usr/bin/g++-$1"