String processing in windows batch files: How to pad value with leading zeros?

问题:

in a Windows cmd batch file (.bat), how do i pad a numeric value, so that a given value in the range 0..99 gets transformed to a string in the range "00" to "99". I.e. I'd like to having leading zeros for values lower than 10.

回答1:

There's a two-stage process you can use:

REM initial setup SET X=5  REM pad with your desired width - 1 leading zeroes SET PADDED=0%X%  REM slice off any zeroes you don't need -- BEWARE, this can truncate the value REM the 2 at the end is the number of desired digits SET PADDED=%PADDED:~-2%

Now TEMP holds the padded value. If there's any chance that the initial value of X might have more than 2 digits, you need to check that you didn't accidentally truncate it:

REM did we truncate the value by mistake? if so, undo the damage SET /A VERIFY=1%X% - 1%PADDED% IF NOT "%VERIFY%"=="0" SET PADDED=%X%  REM finally update the value of X SET X=%PADDED%

Important note:

This solution creates or overwrites the variables PADDED and VERIFY. Any script that sets the values of variables which are not meant to be persisted after it terminates should be put inside SETLOCAL and ENDLOCAL statements to prevent these changes from being visible from the outside world.

回答2:

If you are confident that the number of digits in your original number is always less than 2, then

set "x=0%x%" set "x=%x:~-2%"

If the number may exceed 2 digits, and you want to pad to 2 digits, but not truncate values larger then 99, then

setlocal enableDelayedExpansion if "%x%" equ "%x:~-2%" (   set "x=0%x%"   set "x=!x:~-2!" )

Or without delayed expansion, using an intermediate variable

set paddedX=0%x% if "%x%" equ "%x:~-2%" set "x=%paddedX:~-2%"

The nice thing about the above algorithms is it is trivial to extend the padding to any arbitrary width. For example, to pad to width 10, simply prepend with 9 zeros and preserve the last 10 characters

set "x=000000000%x%" set "x=%x:~-10%"

TO prevent truncating

set paddedX=000000000%x% if "%x%" equ "%x:~-10%" set "x=%paddedX:~-10%"

回答3:

The single line

IF 1%Foo% LSS 100 SET Foo=0%Foo%

will get you what you want for numbers in the range that you specify. It does not change values in the subset 0-9 if they are already single-padded.

回答4:

Previous answers had explained all the existent methods to pad a value with left zeros; I just want to add a small trick I used to do that in an easier way. What had not been enough mentioned in previous answers is that in most cases, the value that will be padded is incremented inside a loop and that the padded value is just used to display it (or similar tasks, like renames). For example, to show values from 00 to 99:

set x=0 :loop    rem Pad x value, store it in padded    set padded=0%x%    set padded=%padded:~-2%    rem Show padded value    echo %padded%    set /A x+=1 if %x% leq 99 goto loop

If this is the case, the value of the variable may be used for both control the loop and display its padded value with no modification if its limits are appropriately translated. For example, to show values from 00 to 99:

set x=100 :loop    rem Show padded value    echo %x:~-2%    set /A x+=1 if %x% leq 199 goto loop

This method works also with any number of left zeros to pad.

Antonio

回答5:

This example uses a for loop to demonstrate, but the logic is the same even if you were to use it without the loop. Just echo a 0 in front if the number is less than 10.

setlocal enabledelayedexpansion for /l %%a in (1,1,40) do ( set n=%%a if !n! lss 10 ( echo 0!n! ) else ( echo !n! ) ) pause >nul

回答6:

OK GUYS i have found a solution, compressing it down as simple as possible.

@echo off title pad numbers set num=0 set zero= 000 :loop @set /a num=%num%+1 if /i %num% GTR 9 set zero= 00 if /i %num% GTR 99 set zero= 0 if /i %num% GTR 999 set zero=  echo %zero%%num% goto loop

this will display your count up number using 4 digits. but the code can be altered to use 2 digits as shown below.

@echo off title pad numbers set num=0 set zero= 0 :loop @set /a num=%num%+1 if /i %num% GTR 9 set zero=  echo %zero%%num% goto loop

if you want to set it as a displayable single variable...

@echo off title pad numbers set num=0 set zero= 0 :loop @set /a num=%num%+1 if /i %num% GTR 9 set zero=  set %zero%%num%=number echo %number% goto loop

if you want it to count up in seconds...

@echo off title pad numbers set num=0 set zero= 0 :loop @set /a num=%num%+1 if /i %num% GTR 9 set zero=  set %zero%%num%=number echo %number% ping localhost -n 2 >nul goto loop

i hope this was a great help ^^

回答7:

@echo off rem . rem   counter example - with and without padding (up to 260 leading 0s which should be enough for most filenames) rem . rem   we assume values given are valid rem   additional error checking could be done to make sure they are numbers rem   and to ensure that starting is less than ending rem   and that the number of ending digits is not greater than the number of padding digits rem . if "%2"=="" (   echo.   echo usage:   %~nx0 [starting number] [ending number] [pad]   echo example: %~nx0  0  19        will output numbers 0 to 19 each on a new line   echo example: %~nx0  3  12  8     will output numbers 3 to 12 each on a new line padded to 8 digits   echo.   goto end   ) rem . setlocal enabledelayedexpansion if "%3"=="" (   for /l %%x in (%1, 1, %2) do (     echo.%%x   ) ) else (   set "mynum="   for /l %%x in (%1, 1, %2) do (     call set "mynum=00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%%x"     call set "mynum=%%mynum:~-%3%%"     call echo.%%mynum%%   ) ) :end

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