Using a variable in replacing a substring in another variable in a loop in Windows batch

Question

The following code is assumed to replace the col3 substring in the variable dir with the value of the variable var in every iteration, but it fails to do so. Does anyone know what is wrong with this code?

code:

@ECHO OFF
SETLOCAL EnableDelayedExpansion
SET dir=col1 col2 col3 col4 col5 col6 col7 col8
FOR /L %%i IN (1,1,5) DO (
SET var=v%%i
SET dir=!dir:col3=%var%!
ECHO !dir!
)
PAUSE

output:

col1 col2  col4 col5 col6 col7 col8
col1 col2  col4 col5 col6 col7 col8
col1 col2  col4 col5 col6 col7 col8
col1 col2  col4 col5 col6 col7 col8
col1 col2  col4 col5 col6 col7 col8

desired output:

col1 col2 v1 col4 col5 col6 col7 col8
col1 col2 v2 col4 col5 col6 col7 col8
col1 col2 v3 col4 col5 col6 col7 col8
col1 col2 v4 col4 col5 col6 col7 col8
col1 col2 v5 col4 col5 col6 col7 col8

you need double delayed expansion: for %%V in (!var!) do SET "dir=!dir:col3=%%V!" — Jeff Wu
– Jeff Wu, Commented Jun 7, 2020 at 6:48

Masa · Accepted Answer · 2020-06-08 05:32:33Z

2

after hours of searching for this problem, I found out that changing the line

SET dir=!dir:col3=%var%!

to

SET dir=%dir:col3=!var!%

solved the issue.

edited Jun 8, 2020 at 5:32

answered Jun 7, 2020 at 8:06

Masa

3005 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

aschipfl Over a year ago

No, this is simply wrong, you need to delay expansion since you are in a loop, and you must expand the inner variable (var) before the outer one (dir)! A possible way is: call set "dir=%%dir:col3=!var!%%"

aschipfl Over a year ago

Sorry, I have to withdraw my previous comment, since in your particular situation your answer actually does provide the solution (accidentally?), because: For every loop iteration, dir is expanded to its original value due to immediate (%-)expansion, with col3 replaced by the literal string !var!; delayed expansion then does the rest and expands !var! by its current value…

aschipfl Over a year ago

My code suggestion however correctly replaces col3 with v1 in the first loop iteration; but for every further iteration, dir expandes to its modified value due to delayed expansion, so there is no more col3 in the string, hence the same value as for the first iteration becomes returned again. Sorry for drawing a hasty and mistaken conclusion!

Collectives™ on Stack Overflow

Using a variable in replacing a substring in another variable in a loop in Windows batch

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related