Batch: Using Number Variable at setting another Variable with concatenate function?

Question

Hopefully someone can help me on this:

I have a batchfile where I want to combine Variables and include a function with a Variable number for the concatenate - for better understanding see attached script:

set vSourcenm=tester.txt

Defines a Variable of the Filetype like ".txt"

set vTargettyp=%vSourcenm:~4%

set vDateTimeStamp=21062016_0908 (Simplified - sets the Date and Time)

set str_len=10 (this one is counted with a loop)

set vTargetnm=%vSourcenm:~0,-%str_len%%_%vDateTimeStamp%%vTargettyp%

The Output of vTargetnm should be :

tester_21062016_0908.txt

Thanks for any hints!

Answer 1

This required the use of delayed expansion to allow the number in the variable to be evaluated before the sub string.

setlocal enabledelayedexpansion

set vSourcenm=tester.txt

rem Defines a Variable of the Filetype like ".txt"
set vTargettyp=%vSourcenm:~4%

rem define how much of the string to remove [equal to the part saved to the extension
set str_len=4

rem Remove the extension from the filename
set vSourcenm=!vSourcenm:~0,-%str_len%!

REM (Simplified - sets the Date and Time)
set vDateTimeStamp=21062016_0908

set vTargetnm=!vSourcenm!_!vDateTimeStamp!!vTargettyp!

echo !vTargetnm!

pause

Your question did not agree with the example output, so the str_len was set to a value of 4 to demonstrate the delayed parsing of the environment variables.

Also the output of the %DATE% and %TIME% is based on system regional settings, so you will want to make sure those are set to what you need them before attempting to parse them in batch.