使用“IF DEFINED变量命令”测试批处理文件中的变量。

但如果您想测试批处理参数，请尝试以下代码以避免棘手的输入(如“1 2”或ab^>cd)

set tmp="%1"
if "%tmp:"=.%"==".." (
    echo empty
) else (
    echo not empty
)

你可以使用

if defined (variable) echo That's defined!
if not defined (variable) echo Nope. Undefined.

脚本1:

输入(“删除引号。”cmd"这是一个测试")

@ECHO OFF

REM Set "string" variable to "first" command line parameter
SET STRING=%1

REM Remove Quotes [Only Remove Quotes if NOT Null]
IF DEFINED STRING SET STRING=%STRING:"=%

REM IF %1 [or String] is NULL GOTO MyLabel
IF NOT DEFINED STRING GOTO MyLabel


REM   OR   IF "." equals "." GOTO MyLabel
IF "%STRING%." == "." GOTO MyLabel

REM GOTO End of File
GOTO :EOF

:MyLabel
ECHO Welcome!

PAUSE

输出(没有，%1不是空的，空的，或NULL):

使用上面的脚本运行("Remove Quotes.cmd")，不带任何参数

输出(%1为空白、空或NULL):

Welcome!

Press any key to continue . . .

注意:如果你在If () ELSE()语句中设置了一个变量，它将在退出If语句后才对DEFINED可用(除非“延迟变量扩展”被启用;一旦启用，请使用感叹号“!”来代替百分比“%”符号}。

例如:

脚本2:

输入(“删除引号。”cmd"这是一个测试")

@ECHO OFF

SETLOCAL EnableDelayedExpansion

SET STRING=%0
IF 1==1 (
  SET STRING=%1
  ECHO String in IF Statement='%STRING%'
  ECHO String in IF Statement [delayed expansion]='!STRING!'
) 

ECHO String out of IF Statement='%STRING%'

REM Remove Quotes [Only Remove Quotes if NOT Null]
IF DEFINED STRING SET STRING=%STRING:"=%

ECHO String without Quotes=%STRING% 

REM IF %1 is NULL GOTO MyLabel
IF NOT DEFINED STRING GOTO MyLabel

REM GOTO End of File
GOTO :EOF

:MyLabel
ECHO Welcome!

ENDLOCAL
PAUSE

输出:

C:\Users\Test>"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd" "This is a Test"  
String in IF Statement='"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd"'  
String in IF Statement [delayed expansion]='"This is a Test"'  
String out of IF Statement='"This is a Test"'  
String without Quotes=This is a Test  

C:\Users\Test>  

注意:它还会从字符串中删除引号。

例如(使用脚本1或2): c:\ users \ test \ documents \批处理文件>"删除引号。cmd"这是"一个"测试"

输出(脚本2):

String in IF Statement='"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd"'  
String in IF Statement [delayed expansion]='"This is "a" Test"'  
String out of IF Statement='"This is "a" Test"'  
String without Quotes=This is a Test  

在脚本2中不带任何参数地执行("Remove Quotes.cmd"):

输出:

Welcome!

Press any key to continue . . .

This way looks correct:

if "%~1" == "" if [%1] == [] echo Argument 1 is really empty.

First filter (if "%~1" == "") из safe way to detect argument is empty or "".
Second filter (if [%1] == []) will skip "" argument.
Remember we have two kind of empty arguments : really empty (nothing) and empty quotes "".
We have to detect both.

Next code takes all arguments "as is" in variable args:

:GetArgs
set args=%1
:ParseArgs
shift /1
if "%~1" == "" if [%1] == [] goto :DoneArgs
set args=%args% %1
goto :ParseArgs
:DoneArgs
if not defined args echo No arguments
if defined args echo Aguments are: %args%

This code correctly process "normal" arguments (simple words, "multiword phrases" or "") with balanced quotes.
Quoted arguments can even contain special chars like "a & b".
But it is still can fail with "abnormal" expressions with unbalanced quotes (do not use them).

空字符串是一对双引号/""，我们可以直接测试长度:

set ARG=%1
if not defined ARG goto nomore

set CHAR=%ARG:~2,1%
if defined CHAR goto goon

然后用双引号测试它的2个字符:

if ^%ARG:~1,1% == ^" if ^%ARG:~0,1% == ^" goto blank
::else
goto goon

这里有一个您可以使用的批处理脚本。我觉得它正好接住了空弦。

这只是一个例子，你只需要根据你的脚本定制上面的2(或3?)步骤。

@echo off
if not "%OS%"=="Windows_NT" goto EOF
:: I guess we need enableExtensions, CMIIW
setLocal enableExtensions
set i=0
set script=%0

:LOOP
set /a i=%i%+1

set A1=%1
if not defined A1 goto nomore

:: Assumption:
:: Empty string is (exactly) a pair of double-quotes ("")

:: Step out if str length is more than 2
set C3=%A1:~2,1%
if defined C3 goto goon

:: Check the first and second char for double-quotes
:: Any characters will do fine since we test it *literally*
if ^%A1:~1,1% == ^" if ^%A1:~0,1% == ^" goto blank
goto goon

:goon
echo.args[%i%]: [%1]
shift
goto LOOP

:blank
echo.args[%i%]: [%1] is empty string
shift
goto LOOP

:nomore
echo.
echo.command line:
echo.%script% %*

:EOF

酷刑测试结果:

.test.bat :: ""  ">"""bl" " "< "">"  (")(") "" :: ""-"  " "( )"">\>" ""
args[1]: [::]
args[2]: [""] is empty string
args[3]: [">"""bl" "]
args[4]: ["< "">"]
args[5]: [(")(")]
args[6]: [""] is empty string
args[7]: [::]
args[8]: [""-"  "]
args[9]: ["( )"">\>"]
args[10]: [""] is empty string

command line:
.test.bat :: ""  ">"""bl" " "< "">"  (")(") "" :: ""-"  " "( )"">\>" ""

不幸的是，我没有足够的声誉来评论或投票目前的答案，我不得不自己写。

最初OP的问题说的是“变量”而不是“参数”，这让人非常困惑，特别是因为这是谷歌中搜索如何测试空白变量的头号链接。自从我最初的答案以来，Stephan编辑了原始问题，以使用正确的术语，但我没有删除我的答案，而是决定留下它来帮助澄清任何困惑，特别是在谷歌仍然派人来这里寻找变量的情况下:

%1不是变量!它是一个命令行参数。

非常重要的区别。后面带数字的单个百分号表示命令行参数，而不是变量。

使用set命令设置变量，并使用2%符号(一个在前面，一个在后面)回收变量。例如%myvar%

要测试空变量，您可以使用“if not defined”语法(显式变量命令不需要任何百分号)，例如:

set myvar1=foo  
if not defined myvar1 echo You won't see this because %myvar1% is defined.  
if not defined myvar2 echo You will see this because %myvar2% isn't defined.

(如果你想测试命令行参数，那么我建议参考jamesdlin的答案。)