Looping through string values using set in Windows cmd

Question

My Windows batch file is supposed to read file names and create a directory that is named according to the filename's 2nd to 5th letter:

for %%f in (.\*.txt) do (
set string=%%~nf
mkdir %string:~2,5%     
)

The value of 'string' is not updated though, i.e. it is the same in each step of the loop. How can I have it updated?

This is the cmd output:

>for %f in (.\*.txt) do (
set string=%~nf
 mkdir le3
)

>(
set string=file1
 mkdir le3
)

>(
set string=file2
 mkdir le3
)
A subdirectory or file le3 already exists.

>(
set string=file3
 mkdir le3
)
A subdirectory or file le3 already exists.

Try consulting the hundreds of articles on SO about delayedexpansion. Essentially, a %var% within a code block is replaced by the value of var when the block is parsed. To access the changing value within a block, you feed first to invoke delayedexpansion using a setlocal enabledelayedexpansion command, and then use !var! to access the dynamic value of the variable. — Magoo
– Magoo, Commented Sep 28, 2016 at 5:31
Thank you for your reply. I consulted several sites, e.g. link and came up with 'SETLOCAL ENABLEDELAYEDEXPANSION for %%f in (.*.txt) do ( set !string!=%%~nf mkdir !string:~2,5! )' - but the delayed expansion does not seem to work yet. Do you have any advice what's wrong? — Joan
– Joan, Commented Sep 28, 2016 at 8:05
set !string!=%%~nf should be set string=%%~nf - you intend to set the variable string, not the variable current content of string — Magoo
– Magoo, Commented Sep 28, 2016 at 13:43

geisterfurz007 · Accepted Answer · 2016-09-28 06:52:36Z

1

The problem you're running into is because of %variable% expansion. The entire FOR statement (including up to the closing parenthesis) is one statement. When it is read, the command processor replaces the %string% variable with whatever string is set to before the SET inside executes. (Actually, you're getting the subset of string starting at the 2nd character and proceeding 5 characters, but that's not really important here. My guess is that you've got %string% set to "file3".)

Anyway, you can fix it by adding SETLOCAL ENABLEDELAYEDEXPANSION at the top and using syntax like !string! instead of %string% inside the FOR.

You could also move the processing of %string% outside of FOR.

Look up HELP SETLOCAL and HELP SET for more.

Also, if you hadn't noticed, you're not getting the second and fifth characters of the filename... As I mentioned, you're getting a substring of (up to) length 5, starting at character 2. Look up HELP SET for more.

edited Sep 28, 2016 at 6:52

geisterfurz007

5,9246 gold badges37 silver badges59 bronze badges

answered Sep 28, 2016 at 5:37

soja

1,60710 silver badges8 bronze badges

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

1 Comment

Joan Over a year ago

I have now enabled delayed expansion and adapted the code: SETLOCAL ENABLEDELAYEDEXPANSION for %%f in (.\*.txt) do ( set !string!=%%~nf mkdir !string:~2,5! ) I understand the idea, also tried setting the quotation marks in different places, but still I don't get the delayed expansion to work - Any ideas?

Compo · Accepted Answer · 2016-09-28 08:47:11Z

0

Nearly, you've got a couple of unnecessary exclamation marks in your last attempt:

SETLOCAL ENABLEDELAYEDEXPANSION
for %%f in (*.txt) do (
    set string=%%~nf
    if not exist "!string:~2,5!\" mkdir "!string:~2,5!"
)

answered Sep 28, 2016 at 8:47

Compo

39k5 gold badges32 silver badges46 bronze badges

1 Comment

Compo Over a year ago

I helps the site and prosective responders if you mark correct answers accordingly.

Collectives™ on Stack Overflow

Looping through string values using set in Windows cmd

2 Answers 2

1 Comment

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related