check_env()

{

    # Check user privilege.

    #检查用户权限

    check_user root

    # Check FQDN hostname.

    #检查主机名是否符合规则

    check_hostname

    # Check config tool: dialog.

    #检查配置工具dialog是否存在

    check_pkg ${BIN_DIALOG} ${PKG_DIALOG}

    ECHO_INFO -n "Checking configuration file: ${IREDMAIL_CONFIG_FILE} ..."

    #

判断配置文件是否存在，默认的安装包下是没有的，应该是用于安装中断后，恢复安装的。

    if [ -f ${IREDMAIL_CONFIG_FILE} ]; then

        if grep '^#EOF$' ${IREDMAIL_CONFIG_FILE} >/dev/null; then

            echo -e " [FOUND]"

            ECHO_QUESTION -n "Use it for mail server setting? [y|N]"

            #

读取已经存在的配置文件

            read_setting ${AUTO_USE_EXISTING_CONFIG_FILE}

            #

给用户一个选择，是用已经存在的配置文件，还是重新安装

case $ANSWER in

                Y|y )

                    ECHO_INFO "Use config file: ${IREDMAIL_CONFIG_FILE} for mail server setting."

                    . ${IREDMAIL_CONFIG_FILE}

                    # Check installation status.

                    # After each component installation was completed, there

                    # should be a variable in ${STATUS_FILE}, e.g.

                    #

                    #   export STATUS_PHP_INSTALLATION='DONE'

                    #   export STATUS_PHP_CONFIGURATION='DONE'

                    #

                    #

判断状态文件是否存在，如果存在则读取状态文件

if [ -f ${STATUS_FILE} ]; then

                        ECHO_INFO "Import installation process status from file: ${STATUS_FILE}."

                        . ${STATUS_FILE}

                    else

                        echo '' > ${STATUS_FILE}

                    fi

                    # Initialize tip file.

                    #

tip文件是安装完成后的一些账号密码文件，此处初始化该文件

if [ ! -f ${TIP_FILE} ]; then

                        cat > ${TIP_FILE} <<EOF

${CONF_MSG}

EOF

                    fi

                    ;;

                N|n|* )

                    ECHO_INFO "Skip configuration file: ${IREDMAIL_CONFIG_FILE}."

                    #

新的安装，CONFIG_VIA_DIALOG在conf/global中定义，他的值是 #export CONFIG_VIA_DIALOG="${DIALOG_DIR}/config_via_dialog.sh" 执行窗口安装程序，开始新的安装

                    . ${CONFIG_VIA_DIALOG}

                    ;;

            esac

        else

            ECHO_INFO "Found, but not finished."

            . ${CONFIG_VIA_DIALOG}

        fi

    else

        ECHO_INFO "[NOT FOUND]"

        . ${CONFIG_VIA_DIALOG}

    fi

    check_runtime_dir

}