Delayed variable expansion inside a substring operation

Question

SETLOCAL EnableDelayedExpansion

SET str=123456789abcdefgh

FOR /l %%x IN (1, 1, 10) DO (

    SET /a intLength=10-%%x

    SET result=!str:~-%%x!
    ECHO "Works as intended: " !result!

    SET result=!str:~-intLength!
    ECHO "Does NOT work as intended: " !result!
)

endlocal

The complete rules for this type of managements are described at [this post](http://stackoverflow.com/questions/10166386/arrays-linked-lists-and-other-data-structures-in-cmd-exe-batch-script/10167990#10167990); you just need to change "array element" by "substring" in that description... — Aacini, Aug 10 '15 at 04:36

score 3 · Answer 1 · answered Aug 09 '15 at 21:53

You're using the literal string intLength instead of the %intLength% variable.

Since you're initializing a variable inside of a for loop, you're going to have to use the !intLength! variation of this variable name. Unfortunately, since you're already using exclamation points to get the substring from str, you can't also use them in that line to get the value of intLength, since you'd then essentially have a variable !str:~!, an unrelated string that batch really isn't going to like, and a !!.

You can get around this by running !intLength! through another for loop and using the %%var variable instead, since you've already shown that that works.

@echo off
setlocal EnableDelayedExpansion

set str=123456789abcdefgh

for /l %%x in (1, 1, 10) DO (

    set /a intLength=10-%%x

    SET result=!str:~-%%x!
    echo Works as intended: !result!

    for /f %%A in ("!intLength!") do SET result=!str:~-%%A!
    echo Now works as intended: !result!
    echo.
)

endlocal

Delayed variable expansion inside a substring operation

1 Answers1