If



ִ


﷨



if [not] errorlevel number command [else expression]


if [not] string1==string2 command [else expression]


if [not] exist filename command [else expression]


չʹ﷨


if [/i] string1 compareop string2 command [else expression]


if cmdextversion number command [else expression]


if defined variable command [else expression]






	not 

	ָֻеΪʱִи

	errorlevel number

	ֻе Cmd.exe еǰһ򷵻شڻ number ˳ʱָ

	command

	ָֻǰʱӦִе

	string1==string2

	ֻе string1  string2 ͬʱָЩֵַ磬%1ַҪʹʺš

	exist filename

	 filename ڣָ

	CompareOp

	ָ 3 ĸıȽ±г compareop Чֵ
	


˵


EQU



NEQ



LSS



LEQ
ڻ


GTR



GEQ
ڻ


	

	/i

	ǿַȽϺԴСд if  string1==string2 ʽʹ/iЩȽͨõģ string1  string2 еɣôַתΪֲҽֱִȽϡ

	cmdextversion number

	ֻе Cmd.exe ġչصڲ汾ŵڻ number ʱָһ汾 1չĹشǿʱڴ˺ϼ 1չʱĬΪãcmdextversion Ϊ档

	defined variable

	 variableָΪ档

	expression

	ָݸ else Ӿκβ

	/?
ʾʾ



ע


  if ָΪ棬ϵͳִиΪ٣ if Ӿеԣͬʱִ else Ӿеκָ
	
	 ֹͣʱ˳롣 errorlevel ˳
    
 ʹ defined variable
	
ʹ defined variable%errorlevel% %cmdcmdline%  %cmdextversion%

 %errorlevel% չ errorlevel ǰֵַʽûΪ ERRORLEVEL ĻͿȡֵķ˵ʹ errorlevel

goto answer%errorlevel%
 :answer0
 echo Program had return code 0
 :answer1
 echo Program had return code 1
 goto end
 :end
 echo done! 

 Ҳʹµ CompareOp Ƚ if %errorlevel% LEQ 1 goto okay

 %cmdcmdline% κ Cmd.exe ֮ǰչݵ Cmd.exe ԴУûΪ cmdcmdline ĻͿȡֵ

 %cmdextversion% չ cmdextversion ǰֵַʽûΪ CMDEXTVERSION ĻͿȡֵ
    
 ʹ else Ӿ
	
 else Ӿ if ͬС磺    IF EXIST filename. (
del filename.
) ELSE (
echo filename.missing.
)

 Ĵ벻ãΪͨһֹ del     IF EXIST filename. del filename.ELSE echo filename.missing

 ãΪ else  if ĩβͬϣ    IF EXIST filename. del filename.
ELSE echo filename.missing

 Ҫȫڵϸʽʹʽԭʼ    IF EXIST filename.(del filename)ELSE echo filename.missing
    








 ûҵļ Product.datʾϢ 

  if not exist product.dat echo Can't find data file 

 ʽ A еĴڼִ淶ʾϢ 

  :begin
 @echo off
 format a:/s
 if not errorlevel 1 goto end
 echo An error occurred during formatting.
:end
 echo End of batch program.

ûгִ󣬽Ϣ

 if ֱӲĿ¼ (NUL) 豸ȷʵÿĿ¼Сˣͨ豸ȷĿ¼Ƿڡ·ɲĿ¼Ĵڣ

  if exist c:mydir\nul goto process 


XOX





