Make your Mac GNU first

__mac_gnu_env.sh

# __mac_gnu_env.sh
# source this script to make your Mac GNU first

if [[ "$OSTYPE" != darwin* ]]; then
    return 1 2>/dev/null || exit 1
fi

pkgs=(bash coreutils findutils gnu-sed grep gawk gnu-tar diffutils make)

# Must be bash
[[ -z "$BASH_VERSION" ]] && {
    echo "This script must be sourced from bash, not zsh."
    return 1 2>/dev/null || exit 1
}

# Check bash version >= 4
if (( ${BASH_VERSION%%.*} < 4 )); then
    echo "Bash 4.0+ is required."
    echo "Install and switch to Bash 4+ before sourcing this script."
    return 1 2>/dev/null || exit 1
fi

# Must be sourced
(return 0 2>/dev/null) || {
    echo "This script must be sourced, not executed."
    echo "Usage: source __mac_gnu_env.sh"
    exit 1
}


# Cache installed packages once
mapfile -t installed_pkgs < <(brew list --formula)

missing=()
for pkg in "${pkgs[@]}"; do
    if ! printf '%s\n' "${installed_pkgs[@]}" | grep -qx "$pkg"; then
        missing+=("$pkg")
        continue
    fi

    prefix="$(brew --prefix "$pkg")"
    # Prepend libexec/gnubin if exists
    if [[ -d "$prefix/libexec/gnubin" ]]; then
        [[ ":$PATH:" != *":$prefix/libexec/gnubin:"* ]] && \
            PATH="$prefix/libexec/gnubin:$PATH"
    fi
    # Prepend bin if exists (some packages install binaries here)
    if [[ -d "$prefix/bin" ]]; then
        [[ ":$PATH:" != *":$prefix/bin:"* ]] && \
            PATH="$prefix/bin:$PATH"
    fi
done

if (( ${#missing[@]} )); then
    echo "Missing packages: ${missing[*]}"
    echo "Install with: brew install ${missing[*]}"
    return 1 2>/dev/null || exit 1
fi

export PATH

echo "GNU tools ready on Mac. PATH updated."