Get LIBC and intrepreter from Dockerfile

libc-from-dockerfile.sh

#!/bin/sh
# dependencies: docker and https://github.com/BurntSushi/ripgrep
libc_renamed=libc.so.6
ldlinux_renamed=ld-linux.so
if distro=$(rg -or '$1$2' -- '(?:--from=|FROM )(debian|ubuntu)(\S+)?' Dockerfile); then
    if container=$(docker container create "$distro"); then
        if libs=$(docker run "$distro" ldd /bin/true); then
            libs=$(printf %s "$libs" | awk 'NF == 4 {print $3}; NF == 2 {print $1}')
            for lib in $libs; do
                case $lib in
                    *libc*.so*     ) docker cp -L "$container":"$lib" "$libc_renamed" ;;
                    *ld-linux*.so* ) docker cp -L "$container":"$lib" "$ldlinux_renamed" ;;
                esac
            done
        else
            # fallback if ldd is not available
            docker cp -L "$container":/lib64/ld-linux-x86-64.so.2 "$ldlinux_renamed"
            docker cp -L "$container":/lib/x86_64-linux-gnu/libc.so.6 "$libc_renamed"
        fi
    fi
fi