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?
WHERE mycommand IF %ERRORLEVEL% NEQ 0 ECHO mycommand wasn't found 
>nul 2>nul behind the mycommand. /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. IF ERRORLEVEL 1 ? 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.
WHERE as I had today :) 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.
(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 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 
WHERE \Windows\System32\cmd.exe => INFO: Could not find files for the given pattern(s). 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" 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.
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 ) 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
PATH. 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 
set JAVA_CMD= for /f %i in ('where java 2^>nul') do ( if exist "%i" set "JAVA_CMD=%i" ) echo %JAVA_CMD% try this.
You can use WHERE for this and specify the /Q parameter to suppress output and return only the exit code:
WHERE /Q myCommand.exe IF ERRORLEVEL 1 ECHO myCommand.exe not found If you're including path information, you either need to use the /R parameter or use : to separate the path and file name. These are essentially the same:
WHERE /R "C:\Windows\System32" cmd.exe WHERE "C:\Windows\System32:cmd.exe" Putting it together based on your question:
WHERE /Q my_command.exe IF ERRORLEVEL 1 ( :: command not found, so don't run it :: maybe show an error message here, can use %ERRORLEVEL% for more information ) ELSE ( :: command exists, so run it with args my_command.exe my_args ) Probably more useful when specifying a path parameter, but when handling a command not found you can use %ERRORLEVEL% for more information. Examples:
| Error Code | Description |
|---|---|
| 1 | Unrecognized command (not found) |
| 2 | Command/file not found in the specified location |
| 3 | Path not found |
| 5 | Access denied |
C:\DOSto be executable with just a basename.