IF NOT %1 GOTO MyLabel // This is invalid syntax
IF "%1" == "" GOTO MyLabel // Works unless %1 has double quotes which fatally kills bat execution
IF %1 == GOTO MyLabel // Gives an unexpected GOTO error.
批处理中判断参数为空，一般做法是：
if "%1"=="" (
)
但这种做法有个缺点，如果参数1是以引号括起来的，比如长文件名，就会失败了出现错误。
正确的做法是：
if "%~1" == "" (
)
例如upload.bat:
@echo off
if "%~2" == "" (
echo usage:
echo %~n0 [serverurl] [filename]
goto end
)
curl -F "file=@%~2" %1
:end