74

I'm writing a bat script in which I invoke a program (such as javac). For simplicity, I want to check if the command exists before I run it. i.e. If the command exists in PATH.

For example, 

if (my_command.exe is a recognized command) then (
  my_command.exe my_args
) else (
  REM Output was probably "'my_command.exe' is not recognized as an internal or external command, operable program or batch file."
  REM Do not run my_command.exe
)

What's the best way to do this in Windows?

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4
  • How will you "recognize" your command ?
    – Rook
    Aug 13, 2010 at 12:56
  • In MS-DOS (true DOS) this was rather simple; you just checked the existence of an exe file in c:\dos; but even then the question remains.
    – Rook
    Aug 13, 2010 at 12:57
  • Sorry for the confusion. I meant essentially a command prompt in Windows. If I type "lkajsflksajdfj" I want to detect it isn't a command. If I type "notepad.exe", it's OK.
    – user46097
    Aug 13, 2010 at 13:18
  • @Rook A search path existed in MS-DOS too (at least in later versions). Executables did not have to live in C:\DOS to be executable with just a basename.
    – jamesdlin
    Apr 12, 2020 at 20:34

10 Answers 10

Reset to default
88 
WHERE mycommand
IF %ERRORLEVEL% NEQ 0 ECHO mycommand wasn't found
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4
  • 18
    If someone doesn't want the output inside the cmd window just add >nul 2>nul behind the mycommand.
    – Sebastian
    Aug 13, 2014 at 13:09
  • Note that there are more output channels than 1 and 2, since 1 stands for output buffer and 2 for error buffer, it depends on how the application was developed, it should work for common apps that ships with Windows, but an specific CLI program could still throwing text when channels 1 and 2 are redirected.
    – ElektroStudios
    Oct 13, 2015 at 14:26
  • 6
    To avoid the output of the where command, one can use the /q (quiet) switch: where /q mycommand
    – Corentor
    Sep 24, 2020 at 13:05
  • There's actually a significant difference between using /q and >nul 2>nul. The first method will only suppress the errors if WHERE exist. The second will suppress absolutely everything, even if the WHERE command doesn't exist or if all PATH variables are cleared.
    – Nelson
    Jan 30 at 1:46
29

The code below should always execute cleanly with no garbage output.

javac -version >nul 2>&1 && (
    echo found javac
) || (
    echo fail
)

Output:

found javac

The same code as a one-liner:

javaz -version >nul 2>&1 && ( echo found javac ) || ( echo fail )

Output:

fail

Note that the order of && and || seems to matter. Also, the command whose existence you are testing for needs to return with an errorlevel <= 0 for this to work. Hopefully the command has /? or --help arguments or, as with java, a version info command.

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3
  • This solution is perfect !
    – robe007
    Jul 8, 2019 at 23:19
  • 1
    Using the other answers in conjunction with this one is what I found best (e.g. replace javac -version with WHERE mycommand)
    – Cestarian
    Dec 20, 2020 at 17:31
  • You should def. have another look onto WHERE as I had today :)
    – Wolf
    Nov 9, 2021 at 17:22
11

The easiest way is to simply run the command, but that has other problems, of course, since maybe you don't want to have a random process started.

for %%x in (my_command.exe) do if not [%%~$PATH:x]==[] set MyCommandFound=1

is an alternative which searchs for the program in the paths listed by the %PATH% environment variable. It's essentially a pure batch version of which(1). It can be made better but essentially this is it.

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2
  • 1
    This is perfect, does exactly what was asked for!
    – Pez Cuckow
    Feb 18, 2013 at 12:26
  • worth noting to people not too familiar with batch scripts: you can easily check multiple commands with this by using (command1.exe;my_other_command.exe) and so on, and use that %%x to get which command it found, e.g. useful to find various versioned programs, so you can set my_cmd=%%x and then instead of my_cmd_5.3.exe do something you just write %my_cmd% do something, can be for example useful for finding several lua or python versions
    – jan6
    Jan 2 at 20:23
5

Some refinements to version below. Test that command exists and suppress unneeded output.

WHERE scp >nul 2>nul
IF %ERRORLEVEL% EQU 0 ECHO scp found
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2
  • where <my_exe> NUL 2>&1 || echo my.exe does not exist && goto :EOF works nicely in scripts
    – Robert
    Nov 10, 2015 at 15:01
  • 1
    NB: This does not work if the file name you want to test includes path information. E.g., WHERE \Windows\System32\cmd.exe => INFO: Could not find files for the given pattern(s).
    – Jonathan Gilbert
    Aug 31, 2018 at 17:25
3

For my situation. The absolute simplest way is using the || or && operator.

my_command.exe -version 2>NUL && echo "my_command exists"

or

my_command.exe -version 2>NUL || echo "my_command doesn't exist"
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1
  • Why don't you redirect stdout too?
    – Joey
    Aug 14, 2010 at 13:09
2

If requiring the installation of extra tools is ok, there's a where command in the resource kits; see Windows equivalent of whereis?.

Otherwise, for versions of Windows that are not too ancient, it's doable in pure cmd, as mentioned in Dos executable lookup except PATH.

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2
  • Thanks for the reponse! Unfortunately, one of the requirements is that it has to run on a vanilla box (XP machines included) - so whereis isn't an option.
    – user46097
    Aug 13, 2010 at 13:16
  • 2
    The second link Gilles gave has a nifty solution that uses FOR and no extra tools.
    – paradroid
    Aug 13, 2010 at 13:19
1

I know this not quite what you're looking for, but with a slight change in logic it should accomplish what you need.

Every command that is run has a return code (aka errorlevel), if the return code is 0 (zero), the command has run successfully, if the return code is greater than 0, something has gone wrong.

See here for more details.

Something like - 

my_command
if (%ERRORLEVEL% > 0) then (
  REM Output was probably "'my_command.exe' is not recognized as an internal or external command, operable program or batch file.  OR SOMETHING WENT WRONG WITH IT."
  REM Do not run my_command.exe
)
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2
  • This is clever, I like it.
    – Shinrai
    Aug 13, 2010 at 22:20
  • Yeah, but its ugly since, if the command is not found it throws a 2 line error. So, a cleaner solution could be found possibly.
    – djangofan
    Nov 28, 2012 at 18:43
0

While all those way might work, why not the built in way?

If exists my_command do echo "my_command exists"

Run "if /?" on the command line for details

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1
  • 7
    This will only look whether a file/directory with that name exists in the current directory. It provides not much of a hint whether a runnable command with that name exists because to determine that you'd have to search the PATH.
    – Joey
    Feb 19, 2013 at 7:18
0

If you are dealing with a broad command that can also be a DOSKEY and if you are fine with executing it and just want to make sure it returns no error (i.e. when it is missing or not declared):

my-command 1>NUL 2>NUL
IF NOT %ERRORLEVEL% == 0 ECHO my-command is faulty or missing
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0 
set JAVA_CMD=
for /f %i in ('where java 2^>nul') do ( if exist "%i" set "JAVA_CMD=%i" )
echo %JAVA_CMD%

try this.

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