临时环境变量设置文件看不懂

有一个Env文件来设置环境变量。
运行命令如下：
#. Env  （. + 空格 + Env）

运行了这个命令以后就可以正常用Make编译工程了。
Env的文件内容如下。现在就是想知道#BASE 到#ENV之间这段代码的意思。

#BASE
if [ -z "$ZSH_NAME" ] && [ "x$0" = "x./environment" ]; then
    echo "Error: This script needs to be sourced. Please run as ". ./Env""
    exit 1
else
    if [ -n "$BASH_SOURCE" ]; then
        SDK_PATH="`dirname $BASH_SOURCE`"
    else
        SDK_PATH="`pwd`"
    fi
    SDK_PATH=`readlink -f "$SDK_PATH"`
    export SDK_PATH
fi

#Env
export PS1="[e[32;1m][am335x][e[0m]:w> "
export PATH=$PATH:${SDK_PATH}/tools/x86-linux-gnu/bin
export OE_QT_INSTALL_PATH=${SDK_PATH}/tools/ARM-linux-gnueabihf/usr/qt-4.8.6
export QMAKESPEC=${OE_QT_INSTALL_PATH}/mkspecs/qws/linux-arm-linux-gnueabihf-g++
export OE_QT_INSTALL_HEADERS=${OE_QT_INSTALL_PATH}/include
export OE_QT_INSTALL_LIBS=${OE_QT_INSTALL_PATH}/lib
export OE_QT_INSTALL_BIN_MOC=${OE_QT_INSTALL_PATH}/bin/moc
export OE_QT_INSTALL_BIN_UIC=${OE_QT_INSTALL_PATH}/bin/uic