Example of delayed expansion in batch file

by

Look at the following examples…

Example 1: The following code DOESN’T use delayed expansion, so the variables in the for loop are expanded only one time. This means that %Count% will always expand to 0 in each iteration of the loop, no matter what we do to it with the set command:

@echo off
set COUNT=0

for %%v in (1 2 3 4) do (
  set /A COUNT=%COUNT% + 1
  echo Count = %COUNT%
)
pause

So this script will output:

Count = 0
Count = 0
Count = 0
Count = 0

This is not how this loop is supposed to work.

Example 2: On the other hand, if we use delayed expansion, we have the following script, which will run as expected.

setlocal ENABLEDELAYEDEXPANSION
set COUNT=0

for %%v in (1 2 3 4) do (
  set /A COUNT=!COUNT! + 1
  echo Count = !COUNT!
)

pause

and, as expected, it will output:

Count = 1
Count = 2
Count = 3
Count = 4

When you use the ENABLEDELAYEDEXPANSION, and expand a variable using ! instead of %, the variable is re-expanded each time, and everything works as it’s supposed to.

More Related Contents:

  1. Variables are not behaving as expected
  2. Windows Batch Variables Won’t Set
  3. Setting a system environment variable from a Windows batch file?
  4. windows batch SET inside IF not working
  5. Set a persistent environment variable from cmd.exe
  6. How can I source variables from a .bat file into a PowerShell script?
  7. How does the Windows Command Interpreter (CMD.EXE) parse scripts?
  8. How do I get current date/time on the Windows command line in a suitable format for usage in a file/folder name?
  9. What is the reason for “X is not recognized as an internal or external command, operable program or batch file”?
  10. How do I run two commands in one line in Windows CMD?
  11. Windows batch: echo without new line
  12. Windows batch files: .bat vs .cmd?
  13. Escape percent in bat file
  14. Windows XP or later Windows: How can I run a batch file in the background with no window displayed?
  15. XCOPY still asking (F = file, D = directory) confirmation
  16. How can two text files be read in parallel by a batch file?
  17. Capture output command CMD
  18. Redirecting Output from within Batch file
  19. Creating a file name as a timestamp in a batch job
  20. Why does only the first line of this Windows batch file execute but all three lines execute in a command shell?
  21. Curl not recognized as an internal or external command, operable program or batch file
  22. How to echo “2” (no quotes) to a file, from a batch script?
  23. Why is the FOR /f loop in this batch script evaluating a blank line?
  24. Rename all files in a directory with a Windows batch script
  25. How do I minimize the command prompt from my bat file
  26. Batch file encoding
  27. Path prefixes \??\ and \\?\
  28. Why doesn’t my stderr redirection end after command finishes? And how do I fix it?
  29. Windows console %DATE% Math
  30. Using echo y as an automated response to a pcp hostkey prompt

Leave a Comment