source: CMT/v1r20p20081118/mgr/cmt_linux_version.sh

# Determine the Linux distribution and version that is being run.
#

export LC_ALL=C
# Check for GNU/Linux distributions
if [ -f /etc/SuSE-release ]; then
    DISTRIBUTION="suse"
    VERSION=`sed  -n '/VERSION/{s#[^0-9]##gp;q}' /etc/SuSE-release`
elif [ -f /etc/UnitedLinux-release ]; then
    DISTRIBUTION="united"
    VERSION=`cat /etc/UnitedLinux-release`
elif [ -f /etc/debian_version ]; then
    DISTRIBUTION="debian"
    VERSION=`cat /etc/debian_version`
    if [ ${VERSION} = "testing/unstable" ]; then
        # The debian testing/unstable version must be translated into
        # a numeric version number, but no number makes sense so just
        # remove the version all together.
        VERSION=""
    fi
elif [ -f /etc/redhat-release ]; then
    read a </etc/redhat-release
    case "$a" in
        Red*Hat*Enterprise*Linux*)
            DISTRIBUTION=rhel
            ;;
        Red*Hat*Linux*)
            DISTRIBUTION=rh
            ;;
        CERN*E*Linux*)
            DISTRIBUTION=cel
            ;;
        Scientific*Linux*)
            DISTRIBUTION=slc
            ;;
#       Scientific*Linux*CERN*)
        *)
            DISTRIBUTION=slc
            ;;
    esac
    VERSION=""
    while [ -n "$a" ]; do
        t="${a#?}"              # all but first char of $a
        c=${a%"${t}"}           # first char of $a
        a="${t}"                # remove first char from $a
        case "$c" in
            [0-9])
            VERSION="${VERSION}${c}"
            ;;
        esac
    done
    case "$VERSION" in
        70|71|72)
            VERSION=73
            ;;
    esac
else
    DISTRIBUTION="unknown"
    VERSION='00'
fi

echo ${DISTRIBUTION}${VERSION}