if [ -n "$HOME" ] && [ -n "$USER" ]; then

    # Set up the per-user profile.
    # This part should be kept in sync with nixpkgs:nixos/modules/programs/shell.nix

    NIX_LINK=$HOME/.nix-profile

    NIX_USER_PROFILE_DIR=@localstatedir@/nix/profiles/per-user/$USER

    if [ -w "$HOME" ]; then
        if ! [ -L "$NIX_LINK" ]; then
            echo "Nix: creating $NIX_LINK" >&2
            if [ "$USER" != root ]; then
                if ! ln -s "$NIX_USER_PROFILE_DIR"/profile "$NIX_LINK"; then
                    echo "Nix: WARNING: could not create $NIX_LINK -> $NIX_USER_PROFILE_DIR/profile" >&2
                fi
            else
                # Root installs in the system-wide profile by default.
                ln -s @localstatedir@/nix/profiles/default "$NIX_LINK"
            fi
        fi

        # Set up a default Nix expression from which to install stuff.
        __nix_defexpr="$HOME"/.nix-defexpr
        [ -L "$__nix_defexpr" ] && rm -f "$__nix_defexpr"
        mkdir -m 0755 -p "$__nix_defexpr"
        if [ "$USER" != root ] && [ ! -L "$__nix_defexpr"/channels_root ]; then
            ln -s @localstatedir@/nix/profiles/per-user/root/channels "$__nix_defexpr"/channels_root
        fi
        unset __nix_defexpr
    fi

    # Append ~/.nix-defexpr/channels to $NIX_PATH so that <nixpkgs>
    # paths work when the user has fetched the Nixpkgs channel.
    export NIX_PATH=${NIX_PATH:+$NIX_PATH:}$HOME/.nix-defexpr/channels

    # Set up environment.
    # This part should be kept in sync with nixpkgs:nixos/modules/programs/environment.nix
    export NIX_PROFILES="@localstatedir@/nix/profiles/default $HOME/.nix-profile"

    # Set $NIX_SSL_CERT_FILE so that Nixpkgs applications like curl work.
    if [ -e /etc/ssl/certs/ca-certificates.crt ]; then # NixOS, Ubuntu, Debian, Gentoo, Arch
        export NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
    elif [ -e /etc/ssl/ca-bundle.pem ]; then # openSUSE Tumbleweed
        export NIX_SSL_CERT_FILE=/etc/ssl/ca-bundle.pem
    elif [ -e /etc/ssl/certs/ca-bundle.crt ]; then # Old NixOS
        export NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt
    elif [ -e /etc/pki/tls/certs/ca-bundle.crt ]; then # Fedora, CentOS
        export NIX_SSL_CERT_FILE=/etc/pki/tls/certs/ca-bundle.crt
    elif [ -e "$NIX_LINK/etc/ssl/certs/ca-bundle.crt" ]; then # fall back to cacert in Nix profile
        export NIX_SSL_CERT_FILE="$NIX_LINK/etc/ssl/certs/ca-bundle.crt"
    elif [ -e "$NIX_LINK/etc/ca-bundle.crt" ]; then # old cacert in Nix profile
        export NIX_SSL_CERT_FILE="$NIX_LINK/etc/ca-bundle.crt"
    fi

    if [ -n "${MANPATH-}" ]; then
        export MANPATH="$NIX_LINK/share/man:$MANPATH"
    fi

    export PATH="$NIX_LINK/bin:$PATH"
    unset NIX_LINK NIX_USER_PROFILE_DIR
fi