Batch script loop

Question

I need to execute a command 100-200 times, and so far my research indicates that I would either have to copy/paste 100 copies of this command, OR use a for loop, but the for loop expects a list of items, hence I would need 200 files to operate on, or a list of 200 items, defeating the point.

I would rather not have to write a C program and go through the length of documenting why I had to write another program to execute my program for test purposes. Modification of my program itself is also not an option.

So, given a command, a, how would I execute it N times via a batch script?

Note: I don't want an infinite loop

For example, here is what it would look like in Javascript:

var i;
for (i = 0; i < 100; i++) {
  console.log( i );
} 

What would it look like in a batch script running on Windows?

Solution 1

for /l is your friend:

for /l %x in (1, 1, 100) do echo %x

Starts at 1, steps by one, and finishes at 100.

WARNING: Use %% instead of %, if it's in a batch file, like:

for /l %%x in (1, 1, 100) do echo %%x

(which is one of the things I really really hate about windows scripting.)

If you have multiple commands for each iteration of the loop, do this:

for /l %x in (1, 1, 100) do (
   echo %x
   copy %x.txt z:\whatever\etc
)

or in a batch file

for /l %%x in (1, 1, 100) do (
   echo %%x
   copy %%x.txt z:\whatever\etc
)

Key:
/l denotes that the for command will operate in a numerical fashion, rather than operating on a set of files
%x is the loops variable
(starting value, increment of value, end condition[inclusive] )

Solution 2

And to iterate on the files of a directory:

@echo off 
setlocal enableDelayedExpansion 

set MYDIR=C:\something
for /F %%x in ('dir /B/D %MYDIR%') do (
  set FILENAME=%MYDIR%\%%x\log\IL_ERROR.log
  echo ===========================  Search in !FILENAME! ===========================
  c:\utils\grep motiv !FILENAME!
)

You must use "enableDelayedExpansion" and !FILENAME! instead of $FILENAME$. In the second case, DOS will interpret the variable only once (before it enters the loop) and not each time the program loops.

Solution 3

Template for a simple but counted loop:

set loopcount=[Number of times]
:loop
[Commands you want to repeat]
set /a loopcount=loopcount-1
if %loopcount%==0 goto exitloop
goto loop
:exitloop

Example: Say "Hello World!" 5 times:

@echo off
set loopcount=5
:loop
echo Hello World!
set /a loopcount=loopcount-1
if %loopcount%==0 goto exitloop
goto loop
:exitloop
pause

This example will output:

Hello World!
Hello World!
Hello World!
Hello World!
Hello World!
Press any key to continue . . .

Solution 4

You could also try this instead of a for loop:

set count=0
:loop
set /a count=%count%+1
(Commands here)
if %count% neq 100 goto loop
(Commands after loop)

It's quite small and it's what I use all the time.

Solution 5

Or you can decrement/increment a variable by the number of times you want to loop:

SETLOCAL ENABLEDELAYEDEXPANSION
SET counter=200
:Beginning
IF %counter% NEQ 0 (
echo %x
copy %x.txt z:\whatever\etc
SET /A counter=%counter%-1
GOTO Beginning
) ELSE (
ENDLOCAL
SET counter=
GOTO:eof

Obviously, using FOR /L is the highway and this is the backstreet that takes longer, but it gets to the same destination.

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