switch gcc versions in debian

gistfile1.sh

#!/bin/sh

versions="6 8"
basetools="cpp gcc-ar gcc-nm gcc-ranlib gcov gcov-dump gcov-tool"
opttools= # "g++ gfortran"
platform="arm-linux-gnueabihf" # FIXME: make it work with "", and multiple platforms

# Test for root rights
if [ $(id -u) -ne 0 ]; then
   echo "This script must be run as root.">&2
   exit 1
fi

# Create list of all needed packages (e.g., gcc-6-arm-linux-gnueabi)
packages=
for v in $versions ; do
    for t in gcc $opttools ; do
        packages="$packages $t-$v-$platform"
    done
done

# Ensure respective versions of the tools are installed
echo "Installing $packages"
apt install $packages

# Remove existing alternatives
for t in gcc $opttools ; do
    update-alternatives --remove-all $t 2>/dev/null
done

# Add everything to the update-alternatives db
for v in $versions ; do
    prio=$(expr $v \* 10)
    slaves=
    for t in $opttools $basetools ; do
        slaves="$slaves --slave /usr/bin/$platform-$t $platform-$t /usr/bin/$platform-$t-$v"
    done
    update-alternatives --install /usr/bin/$platform-gcc $platform-gcc /usr/bin/$platform-gcc-$v $prio $slaves
done

# Choose the newest version by default
update-alternatives --auto $platform-gcc
echo "$platform-gcc has been set to $(realpath $(which $platform-gcc))"
echo "Use \"sudo update-alternatives --config $platform-gcc\" to change it."