install-guard.sh

#!/bin/sh
# This scripts downloads and installs cfn-guard latest version from github releases
# It detects platforms, downloads the pre-built binary for the latest version installs
# it in the ~/.guard/$MAJOR_VER/cfn-guard-v$MAJOR_VER-$OS_TYPE-latest/cfn-guard and symlinks ~/.guard/bin
# to the latest one

main() {
    if ! ( check_cmd curl || check_cmd wget ); then
        err "need 'curl' or 'wget' (command not found)"
    fi
    need_cmd awk
    need_cmd mkdir
    need_cmd rm
    need_cmd uname
    need_cmd tar
    need_cmd ln

    get_os_type
    get_latest_release |
        while read -r MAJOR_VER; read -r VERSION; do
            mkdir -p ~/.guard/"$MAJOR_VER" ~/.guard/bin ||
                err "unable to make directories ~/.guard/$MAJOR_VER, ~/.guard/bin"
            get_os_type
            download https://github.com/aws-cloudformation/cloudformation-guard/releases/download/"$VERSION"/cfn-guard-v"$MAJOR_VER"-"$OS_TYPE"-latest.tar.gz > /tmp/guard.tar.gz ||
                err "unable to download https://github.com/aws-cloudformation/cloudformation-guard/releases/download/$VERSION/cfn-guard-v$MAJOR_VER-$OS_TYPE-latest.tar.gz"
            tar -C ~/.guard/"$MAJOR_VER" -xzf /tmp/guard.tar.gz ||
                err "unable to untar /tmp/guard.tar.gz"
            ln -sf ~/.guard/"$MAJOR_VER"/cfn-guard-v"$MAJOR_VER"-"$OS_TYPE"-latest/cfn-guard ~/.guard/bin ||
                err "unable to symlink to ~/.guard/bin directory"
            ~/.guard/bin/cfn-guard help ||
                err "cfn-guard was not installed properly"
            echo "Remember to SET PATH include PATH=\${PATH}:~/.guard/bin"
        done
}

get_os_type() {
    _ostype="$(uname -s)"
    case "$_ostype" in
        Darwin)
            OS_TYPE="macos"
            ;;

        Linux)
            # IS this RIGHT, we need to build for different ARCH as well.
            # Need more ARCH level detections
            OS_TYPE="ubuntu"
            ;;

        *)
            err "unsupported OS type $_ostype"
            ;;
    esac
}


get_latest_release() {
    download https://api.github.com/repos/aws-cloudformation/cloudformation-guard/releases/latest |
    awk -F '"' '/tag_name/ { print $4 }' |
    awk -F '.' '{ print $1 "\n" $0 }'
}

err() {
    echo "$1" >&2
    exit 1
}

need_cmd() {
    if ! check_cmd "$1"; then
        err "need '$1' (command not found)"
    fi
}

check_cmd() {
    command -v "$1" > /dev/null 2>&1
}

download()
{
    if check_cmd curl; then
        curl -fsSL "$1"
    else
        wget -qO- "$1"
    fi
}


main