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【DOS批处理】函数定义和用法
本文主要讲述如下几个问题:
1.什么是函数,怎么创建函数?
2.怎么调用一个函数?
3.函数是怎么工作的?
4.怎么向函数传递参数?
5.函数怎么返回值和返回一个局部变量的值。
一、创建函数(什么是函数)
在batch script 中的函数以一个标签开始,并以goto:eof结束,如下:
script
:myDosFunc - 函数的开始,用一个标签标识echo. 函数体,可以执行很多命令echo. GOTO:EOF
二、调用函数
Script: 01.
call:myDosFunc
三、函数怎么工作
调用函数的脚本将其分成两部分。
1.main script: 从第一行开始并且以 GOTO:EOF命令结束
2.函数部分:由多个函数组成,由main script调用。
SCRIPT:
@echo offecho.开始调用函数call:myDosFuncecho.从函数返回myDosFuncecho.&pause&goto:eof::--------------------------------------------------------::-- 函数部分开始::--------------------------------------------------------:myDosFunc - here starts my function identified by it`s labelecho. here the myDosFunc function is executing a group of commandsecho. it could do a lot of thingsgoto:eof
三、怎么传递参数,并且在函数中获取参数的值
1.用空格或者逗号将参数分开
2.用双引号将带有空格的字符串参数括起来
call:myDosFunc 100 YeePEEcall:myDosFunc 100 "for me"call:myDosFunc 100,"for me"
获取参数,采用%1~%9来获取每个参数的值。%0,表示批处理文件本身
:myDosFunc - here starts myDosFunc identified by it`s labelecho.echo. here the myDosFunc function is executing a group of commandsecho. it could do %~1 of things %~2.goto:eof
带参数的脚本
@echo offecho.going to execute myDosFunc with different argumentscall:myDosFunc 100 YeePEEcall:myDosFunc 100 "for me"call:myDosFunc 100,"for me"call:myDosFunc 100,for meecho.&pause&goto:eof::--------------------------------------------------------::-- Function section starts below here::--------------------------------------------------------:myDosFunc - here starts my function identified by it's labelecho.echo. here the myDosFunc function is executing a group of commandsecho. it could do %~1 of things %~2.goto:eof
四、函数返回值
1、调用命令不像其他语言那样能有返回值,最常用的做法是在函数中将该值保存在全局变量中,调用结束后
直接用该全局变量。如下:
Usage:
set "var1=some hopefully not important string"echo.var1 before: %var1%call:myGetFuncecho.var1 after : %var1%
Script:
:myGetFunc - get a valueset "var1=DosTips"goto:eof
脚本输出如下:
var1 before: some hopefully not important string
var1 after : DosTips
2、通过引用返回值,调用者通过传递一个变量给函数来存储返回值
Usage:
call:myGetFunc var1echo.var1 after : %var1%
Script:
:myGetFunc - passing a variable by referenceset "%~1=DosTips"goto:eof
脚本输出如下:
var1 after : DosTips
完整脚本:
@echo offset "var1=CmdTips"echo.var1 before: %var1%call:myGetFunc var1echo.var1 after : %var1%echo.&pause&goto:eof::--------------------------------------------------------::-- Function section starts below here::--------------------------------------------------------:myGetFunc - passing a variable by referenceset "%~1=DosTips"goto:eof
五、函数的局部变量
怎么保证局部变量和全局变量不冲突,SETLOCAL命令能让处理器当做是局部变量,用ENDLOCAL解除局部变量。
ENDLOCAL 会被自动调用,当批处理执行到文件末尾的时候,即GOTO:EOF。SETLOCAL可以很好的保护函数内与外面的变量不会冲突。
@echo offset "aStr=Expect no changed, even if used in function"set "var1=No change for this one. Now what?"echo.aStr before: %aStr%echo.var1 before: %var1%call:myGetFunc var1echo.aStr after : %aStr%echo.var1 after : %var1%echo.&pause&goto:eof::--------------------------------------------------------::-- Function section starts below here::--------------------------------------------------------:myGetFunc - passing a variable by referenceSETLOCALset "aStr=DosTips"set "%~1=%aStr%"ENDLOCALgoto:eof
脚本输出:
aStr before: Expect no changed, even if used in function
var1 before: No change for this one. Now what?
aStr after : Expect no changed, even if used in function
var1 after : No change for this one. Now what?
返回局部变量
----怎么跳过ENDLOCAL的屏障,返回局部变量值?
采用”变量扩充“,在SETLOCAL与ENDLOCAL之间的全局变量的值会备份,当退出ENDLOCAL,该值将恢复。让命令处理器来执行ENDLOCAL 和SET命令。
@echo offset "aStr=Expect no changed, even if used in function"set "var1=Expect changed"echo.aStr before: %aStr%echo.var1 before: %var1%call:myGetFunc var1echo.aStr after : %aStr%echo.var1 after : %var1%echo.&pause&goto:eof::--------------------------------------------------------::-- Function section starts below here::--------------------------------------------------------:myGetFunc - passing a variable by referenceSETLOCALset "aStr=DosTips"( ENDLOCAL set "%~1=%aStr%")goto:eof:myGetFunc2 - passing a variable by referenceSETLOCALset "aStr=DosTips"ENDLOCAL&set "%~1=%aStr%" &rem THIS ALSO WORKS FINEgoto:eof
脚本输出:
aStr before: Expect no changed, even if used in function
var1 before: Expect changed
aStr after : Expect no changed, even if used in function
var1 after : DosTips
六、编写递归函数
让函数局部变量的变换对调用者是可见的,循环调用函数,让变量可重用。下面编写一个函数计算Fibonacci数列。
@echo offset "fst=0"set "fib=1"set "limit=1000000000"call:myFibo fib,%fst%,%limit%echo.The next Fibonacci number greater or equal %limit% is %fib%.echo.&pause&goto:eof::--------------------------------------------------------::-- Function section starts below here::--------------------------------------------------------:myFibo -- calculate recursively the next Fibonacci number greater or equal to a limit:: -- %~1: return variable reference and current Fibonacci number:: -- %~2: previous value:: -- %~3: limitSETLOCALset /a "Number1=%~1"set /a "Number2=%~2"set /a "Limit=%~3"set /a "NumberN=Number1 + Number2"if /i %NumberN% LSS %Limit% call:myFibo NumberN,%Number1%,%Limit%(ENDLOCAL IF "%~1" NEQ "" SET "%~1=%NumberN%")goto:eof
七、总结,定义一个标准的dos batch script function
:myFunctionName -- function description here:: -- %~1: argument description hereSETLOCALREM.--function body hereset LocalVar1=...set LocalVar2=...(ENDLOCAL & REM -- RETURN VALUES IF "%~1" NEQ "" SET %~1=%LocalVar1% IF "%~2" NEQ "" SET %~2=%LocalVar2%)GOTO:EOF
【DOS批处理】函数定义和用法