Logical operators (“and”, “or”) in DOS batch

Question

How would you implement logical operators in DOS Batch files?

Answer 1

It's just as easy as the following:

AND> if+if

if "%VAR1%"=="VALUE" if "%VAR2%"=="VALUE" *do something*

OR> if // if

set BOTH=0
if "%VAR1%"=="VALUE" if "%VAR2%"=="VALUE" set BOTH=1
if "%BOTH%"=="0" if "%VAR1%"=="VALUE" *do something*
if "%BOTH%"=="0" if "%VAR2%"=="VALUE" *do something*

I know that there are other answers, but I think that the mine is more simple, so more easy to understand. Hope this helps you! ;)

Answer 2

De Morgan's laws allow us to convert disjunctions ("OR") into logical equivalents using only conjunctions ("AND") and negations ("NOT"). This means we can chain disjunctions ("OR") on to one line.

This means if name is "Yakko" or "Wakko" or "Dot", then echo "Warner brother or sister".

set warner=true
if not "%name%"=="Yakko" if not "%name%"=="Wakko" if not "%name%"=="Dot" set warner=false
if "%warner%"=="true" echo Warner brother or sister

This is another version of paxdiablo's "OR" example, but the conditions are chained on to one line. (Note that the opposite of leq is gtr, and the opposite of geq is lss.)

set res=true
if %hour% gtr 6 if %hour% lss 22 set res=false
if "%res%"=="true" set state=asleep

Answer 3

Slight modification to Andry's answer, reducing duplicate type commands:

set "A=1" & set "B=2" & call :IF_AND
set "A=1" & set "B=3" & call :IF_AND
set "A=2" & set "B=2" & call :IF_AND
set "A=2" & set "B=3" & call :IF_AND

echo.

set "A=1" & set "B=2" & call :IF_OR
set "A=1" & set "B=3" & call :IF_OR
set "A=2" & set "B=2" & call :IF_OR
set "A=2" & set "B=3" & call :IF_OR

goto :eof

:IF_OR

(if /i not %A% EQU 1 (
   if /i not %B% EQU 2 (
      echo FALSE-
      type 2>nul
   )
)) && echo TRUE+

goto :eof

:IF_AND


(if /i %A% EQU 1 (
   if /i %B% EQU 2 (
      echo TRUE+
      type 2>nul
   )
)) && echo FALSE-

goto :eof

Answer 4

If you have interested to write an if+AND/OR in one statement, then there is no any of it. But, you can still group if with &&/|| and (/) statements to achieve that you want in one line w/o any additional variables and w/o if-else block duplication (single echo command for TRUE and FALSE code sections):

@echo off

setlocal

set "A=1" & set "B=2" & call :IF_AND
set "A=1" & set "B=3" & call :IF_AND
set "A=2" & set "B=2" & call :IF_AND
set "A=2" & set "B=3" & call :IF_AND

echo.

set "A=1" & set "B=2" & call :IF_OR
set "A=1" & set "B=3" & call :IF_OR
set "A=2" & set "B=2" & call :IF_OR
set "A=2" & set "B=3" & call :IF_OR

exit /b 0

:IF_OR
( ( if %A% EQU 1 ( type nul>nul ) else type 2>nul ) || ( if %B% EQU 2 ( type nul>nul ) else type 2>nul ) || ( echo.FALSE-& type 2>nul ) ) && echo TRUE+

exit /b 0

:IF_AND
( ( if %A% EQU 1 ( type nul>nul ) else type 2>nul ) && ( if %B% EQU 2 ( type nul>nul ) else type 2>nul ) && echo.TRUE+ ) || echo.FALSE-


exit /b 0

Output:

TRUE+
FALSE-
FALSE-
FALSE-

TRUE+
TRUE+
TRUE+
FALSE-

The trick is in the type command which drops/sets the errorlevel and so handles the way to the next command.

Answer 5

The following examples show how to make an AND statement (used for setting variables or including parameters for a command).

To close the CMD window and start Notepad:

exit & start notepad.exe

To set variables x, y, and z to values if the variable 'a' equals blah.

if %a% equ blah set x=1 & set y=2 & set z=3

Hope that helps!

Answer 6

Try the negation operand - 'not'!

Well, if you can perform 'AND' operation on an if statement using nested 'if's (refer previous answers), then you can do the same thing with 'if not' to perform an 'or' operation.

If you haven't got the idea quite as yet, read on. Otherwise, just don't waste your time and get back to programming.

Just as nested 'if's are satisfied only when all conditions are true, nested 'if not's are satisfied only when all conditions are false. This is similar to what you want to do with an 'or' operand, isn't it?

Even when any one of the conditions in the nested 'if not' is true, the whole statement remains non-satisfied. Hence, you can use negated 'if's in succession by remembering that the body of the condition statement should be what you wanna do if all your nested conditions are false. The body that you actually wanted to give should come under the else statement.

And if you still didn't get the jist of the thing, sorry, I'm 16 and that's the best I can do to explain.