For loop in CMD… how to loop A to Z (for drive let

Question

How can I get drive the valid drive letters from A to Z with the "for loop" in windows command line (cmd.exe)?

Example, list all files in a drive root folder, should be something like (conceptual):

for %f in (A..Z) do dir %f:\

or aproximating existing functionality:

for /L in (A, Z, 1) do echo %f:\

Answer 1

To loop through all drive letters without explicitly stating them you could use forfiles (which is delivered with all Windows versions past Vista, I believe) and its capability to expand hex. codes 0xHH, together with exit to set the exit code and the hidden variable =ExitCode to convert the exit code to a hexadecimal value, like in this example code:

@echo off
for /L %%C in (0x41,1,0x5A) do (
    cmd /C exit %%C
    for /F %%D in ('
        forfiles /P "%~dp0." /M "%~nx0" /C "cmd /C echo 0x%%=ExitCode:~-2%%"
    ') do echo %%D:\
)

This is quite slow though, because there are several cmd instances opened and closed.

---

To loop through all available drives, including network drives and also such established by subst, you could use the following code, based on wmic:

for /F "skip=1" %%C in ('wmic LogicalDisk get DeviceID') do for /F %%D in ("%%C") do echo %%D\

To loop through all local drives, you could use the following code, again based on wmic:

for /F "skip=1" %%C in ('wmic Volume where "DriveLetter is not Null" get DriveLetter') do for /F %%D in ("%%C") do echo %%D\

To loop through all local drives, but based on mountvol, you could use the following code instead:

for /F %%C in ('mountvol ^| find ":\"') do echo %%C

Finally, for the sake of completeness, to loop through all drives that have been established by subst, use the this code:

for /F "delims=\" %%C in ('subst') do echo %%C\

Answer 2

Here you go, you can iterate through all drives with a for loop now.

@echo off
setlocal enableDelayedExpansion
cls

REM getting the output from fsutil fsinfo drives and putting it in the ogdrives variable
FOR /F "tokens=* USEBACKQ" %%F IN (`fsutil fsinfo drives`) DO (
SET ogdrives=%%F
)
REM making the drives variable the same as the ogdrives variable so it can be manipulated
set drives=!ogdrives!

REM formating the out so that it looks like 1+1+1+... for every drive that is connected
set drives=!drives:Drives^: =!
set drives=!drives:^:\=1!
set drives=!drives: =+!

REM still formating to find out how many drives there are, this bit gets rid of any letters there are
set charms=0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
for /L %%N in (10 1 62) do (
for /F %%C in ("!charms:~%%N,1!") do (
set drives=!drives:%%C=!
)
)
REM last for finding out the number, this removes the last characters since it is a leading + that shouldnt be there
set drives=!drives:~0,-1!
REM num is now the variable that contains the number of drives connected
set /a num=!drives!

REM reseting the drives variable to the original output so it can be manipulated again
set drives=!ogdrives!
REM this time it is being formated to list the drives as a solid string of drive letters like ABCD
set drives=!drives:Drives^: =!
set drives=!drives:^:\=!
set drives=!drives: =!

REM this is to iterate through that string of drive letters to seperate it into multiple single letter variables that are correlated to a number so they can be used later
:loop
REM the iter variable holds how many times this has looped so that when it hits the final drive it can exit
set /a iter=!iter!+1
REM the pos variable is the position in the string of drive letters that needs to be taken out for this iteration
set /a pos=!iter!-1

REM this sets the driveX variable where X is the drives correlated number to the letter of that drive from the long string of drive letters by using the pos variable
set drive!iter!=!drives:~%pos%,1!

REM this is checking to see if all drives have been assigned a number and if it has it will exit the loop
if !iter!==!num! goto oloop
goto loop
:oloop


REM drives are stored in variables %driveX% where X represents the drive number
REM the number of drives are stored in the %num% variable
REM below is an example for iterating through drives

REM this is an example of how to use the information gathered to iterate through the drives
REM we are using a for loop from 1 to the number of drives connected
for /L %%n in (1 1 !num!) do (
REM for every drive that is connected this will be ran
REM %%n contains a number which will increase since its a for loop
REM the drive driveX variable can then be used since drive1=A and drive2=B etc
echo drive %%n is !drive%%n!
REM you can see how i have embedded a variable inside a variable to create an array of sorts.
)
pause
exit
REM the actual variable names are drive1 drive2 drive3 but so that we can iterate through them we can just use a for loop and put the number in the variable
REM one way you can use this is with the where command since it will only search one drive at a time
REM you can do this like this 

for /L %%n in (1 1 !num!) do (

where /R !drive%%n!:\ *.txt

)

REM this will return a list of all txt files in the entire system since it searches all drives.

Answer 3

To add onto the answer of aschipfl, here is how you can programatically generate a string variable that contains all the alphabet letters for iterating through, (both upper and lower) though its kinda clunky:

@ECHO OFF
setlocal enabledelayedexpansion
FOR /F "tokens=1,2" %%a  IN ('ECHO 65 90 ^& ECHO 97 122') DO (
FOR /L %%i IN (%%a,1,%%b) DO (cmd /c exit %%i & set alpha=!alpha! !=exitcodeAscii!))
echo %alpha%
pause  

I was working on doing this to use with findstr, but it will work here as well. If you want to only generate the upper or lower letters I'll leave that exercise to the reader. After generating the string this way you can use the variable in aschipfl's answer above:

for %%p in (%alpha%) do if not exist %%p:\nul set FREEDRIVELETTER=%%p

Answer 4

Close, but it's more like this.

for %%p in (A B C D E F G H I J K L M N O P Q R S T U V W X Y Z) do if not exist %%p:\nul set FREEDRIVELETTER=%%p

EDIT: Here is a powershell way, not sure if off-topic for your needs

Loops the Upper Case Alphabet

65..90 | foreach {[char]$_;Write-Host "Do Something"}

or Lower Case Alphabet

97..122 | foreach {[char]$_;Write-Host "Do Something"}

Maybe this will work from a batch file.

@ECHO OFF
start /b /wait powershell.exe "97..122 | foreach {$a=[char]$_ ;dir $a:\}"
PAUSE

Answer 5

The best way I found was using WMI

wmic volume get "caption"

gives just the valid drive letters... Still searching for a way to do it without external tools/libs/modules (like WMI)