How to find if a string is in a list of strings in a DOS batch file

Question

I'd like to check if an argument to a batch file is valid based on a list of strings.

For example:

IF %1 IN validArgument1, validArgument2, validArgument3 SET ARG=%1

This would set ARG to one of the valid arguments only if it matched. Ideally case insensitively.

Solution 1

You may also use the array approach:

setlocal EnableDelayedExpansion

set arg[1]=validArgument1
set arg[2]=validArgument2
set arg[3]=validArgument3

for /L %%i in (1,1,3) do if /I "%1" equ "!arg[%%i]!" SET "ARG=!arg[%%i]!"

In my opinion, this method is clearer and simpler to manage with multiple options. For example, you may create the array of valid arguments this way:

set i=0
for %%a in (validArgument1 validArgument2 validArgument3) do (
   set /A i+=1
   set arg[!i!]=%%a
)

---

Another possibility is to define a variable for each valid argument:

for %%a in (validArgument1 validArgument2 validArgument3) do set %%a=1

... and then just check the parameter this way:

if defined %1 (
   echo %1 is valid option...
   SET ARG=%1
)

Solution 2

A robust method is to use delayed expansion

setlocal enableDelayedExpansion
set "validArgs=;arg1;arg2;arg3;"
if "!validArgs:;%~1;=!" neq "!validArgs!" set ARG=%1

It can also be done using CALL along with normal expansion, but it is more likely to fail, depending on the value of the parameter.

set "validArgs=;arg1;arg2;arg3;"
call set "test=%%validArgs:;%~1;=%%"
if "%test%" neq "%validArgs%" set ARG=%1

Both techniques above have a limitation that no valid arg can contain = and args must not start with *.

You could also use the following brute force method as long as none of the valid args contain * ? , ; = or <space>

set "validArgs=arg1;arg2;arg3"
for %%A in (%validArgs%) if /i "%~1"=="%%A" set ARG=%1

You might want to have a look at this argument parser. You could adapt that code, or it might spark some ideas for your own unique strategy.