How do I increment a DOS variable in a FOR F loop

Question

I m trying to read text lines from a file  and increment a counter so I can eventually simulate an array in DOS   I d like to be able to store the lines of text in a DOS array for further processing   My current attempt is   set TEXT T  myfile txt   set  a c 1  FOR  F  tokens 1 usebackq    i in   TEXT T   do   set  a c c 1 echo   i    c      But the variable c is not incrementing  it stays at 1   Suggestions welcome   Thanks  Mike

User · Answer

set TEXT T  myfile txt  set  a c 1  FOR  F  tokens 1 usebackq    i in   TEXT T   do       set  a c  1     set OUTPUT FILE NAME output  c  txt     echo Output file is  OUTPUT FILE NAME      echo   i   c

User · Answer

What about this simple code  works for me and on Windows 7  set cntr 1  begin echo  cntr  set  a cntr  cntr  1 if  cntr  EQU 1000 goto end goto begin   end

User · Answer

I would like to add that in case in you create local variables within the loop  they need to be expanded using the bang    notation as well  Extending the example at https   stackoverflow com a 2919699 above  if we want to create counter-based output filenames  set TEXT T  myfile txt   set  a c 1  setlocal ENABLEDELAYEDEXPANSION  FOR  F  tokens 1 usebackq    i in   TEXT T   do       set  a c c 1     set OUTPUT FILE NAME output  c  txt     echo Output file is  OUTPUT FILE NAME      echo   i   c     endlocal

User · Answer

Or you can do this without using Delay   set  a  counter 0    -  your for loop here  do      statement1    statement2    call  increaseby1      increaseby1 set  a  counter  1

User · Answer

The problem with your code snippet is the way variables are expanded  Variable expansion is usually done when a statement is first read  In your case the whole FOR loop and its block is read and all variables  except the loop variables are expanded to their current value   This means  c  in your echo   i   c  expanded instantly and so is actually used as echo   i  1 in each loop iteration   So what you need is the delayed variable expansion  Find some good explanation about it here   Variables that should be delay expanded are referenced with  VARIABLE  instead of  VARIABLE   But you need to activate this feature with setlocal ENABLEDELAYEDEXPANSION and reset it with a matching endlocal   Your modified code would look something like that   set TEXT T  myfile txt   set  a c 1  setlocal ENABLEDELAYEDEXPANSION  FOR  F  tokens 1 usebackq    i in   TEXT T   do     set  a c c 1    echo   i   c     endlocal

[arrays] How do I increment a DOS variable in a FOR /F loop?

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