如何在DOS批处理文件中实现逻辑操作符?


当前回答

Athul Prakash (age 16 at the time) gave a logical idea for how to implement an OR test by negating the conditions in IF statements and then using the ELSE clause as the location to put the code that requires execution. I thought to myself that there are however two else clauses usually needed since he is suggesting using two IF statements, and so the executed code needs to be written twice. However, if a GOTO is used to skip past the required code, instead of writing ELSE clauses the code for execution only needs to be written once.

下面是一个可测试的例子,我将如何实现Athul Prakash的否定逻辑来创建一个OR。

在我的例子中,如果某人有坦克执照或者正在服兵役,他就可以开坦克。在两个提示中输入true或false,你将能够看到逻辑是否允许你驾驶坦克。

@ECHO OFF
@SET /p tanklicence=tanklicence:
@SET /p militaryservice=militaryservice:

IF /I NOT %tanklicence%==true IF /I NOT %militaryservice%==true GOTO done

ECHO I am driving a tank with tanklicence set to %tanklicence% and militaryservice set to %militaryservice%

:done

PAUSE

其他回答

只有OR部分是棘手的,但对于一个包含NOT OR AND的普通布尔表达式,唯一好的解决方案是:

REM if A == B OR C == C then yes

(call :strequ A B || call :strequ C C) && echo yes
exit /b

:strequ
if "%1" == "%2" exit /b 0
exit /b 1

IF语句不支持逻辑运算符AND和OR。 级联IF语句构成隐式连词:

IF Exist File1.Dat IF Exist File2.Dat GOTO FILE12_EXIST_LABEL

如果存在File1.Dat和File2.Dat,则跳转到标签FILE12_EXIST_LABEL。

参见:IF /?

下面的例子展示了如何创建AND语句(用于为命令设置变量或包含参数)。

启动记事本并关闭CMD窗口:

start notepad.exe & exit

如果变量'a' = blah,则设置变量x、y和z的值。

IF "%a%"=="blah" (set x=1) & (set y=2) & (set z=3)

希望有帮助!

如果你需要else子句,你可以使用下面的语法:

AND:

if %v1% == a (if %v2% == b (echo yes) else echo no) else echo no

OR:

if %v1% == a (echo yes) else (if %v2% == b (echo yes) else echo no)

你可以用嵌套条件做和:

if %age% geq 2 (
    if %age% leq 12 (
        set class=child
    )
)

or:

if %age% geq 2 if %age% leq 12 set class=child

你可以用一个单独的变量:

set res=F
if %hour% leq 6 set res=T
if %hour% geq 22 set res=T
if "%res%"=="T" (
    set state=asleep
)

注意,这个答案是针对cmd批处理语言定制的,在Windows中可以找到。你提到了“DOS批处理”,但是,基于几点,我认为前者的选择是一个安全的赌注(1)。

如果你真的是指原始的MS-DOS批处理语言,你应该记住If语句要简单得多,你可能需要使用If语句的块…Goto表示控制流,而不是(例如)括号或其他。


(1)以下几点支持:

The presence of the cmd and windows-console tags; Prior experience of some people failing to recognise the very real difference between cmd and MS-DOS batch languages, and conflating DOC with the cmd terminal window; The question using the more generic "DOS" rather than specifically "MS-DOS" (where "DOS" could possibly be any disk operating system; The fact this is Stack Overflow rather than the retro-computing sister site, where a question about MS-DOS would be way more appropriate (I'm often on that site as well, it's nice for those of us who remember and appreciate computer history); and The (eventual) acceptance of the answer by the original asker, indicating that the solution worked.