What is the easiest way to reset ERRORLEVEL to zero?

Question

I have a post-build event that runs some commands for a c# project. The last command would sometimes cause the ERRORLEVEL value not equals to zero and then the build fails.

I want to append an extra line of command to always set the ERRORLEVEL value to zero. What is the most convenient way to do that?

Answer 1

if you use exit /b 0 you can return an errorlevel 0 from within a child batch script without also exiting the parent.

Answer 2

Seems to do the trick:

ver > nul

Not everything works, and it is not clear why. For example, the following do not:

echo. > nul
cls > nul

Answer 3

In a pre- or post-build event, if the return code of an executable is greater than zero, and the call to the executable is not the last line of the pre- or post-build event, a quick way to mute it and avoid triggering a check for a non-zero errorlevel is to follow the failing line with a line that explicitly returns zero:

cmd /c "exit /b 0"

This is essentially a generic combination of the previously-mentioned solutions that will work with more than just the last line of a pre- or post-build event.

Answer 4

I personally use this:

cd .

Works even in unix shell.

But, this one might be a bit faster:

type nul>nul

Because Process Monitor shows QueryDirectory calls on cd .

PS: cd . has another nice side effect in the unix shell. It does restore recreated working directory in the terminal if it has been opened before the erase.

Update:

And that is a bit more faster:

call;

Any windows command to find if a file is in use or not ? :
https://www.dostips.com/forum/viewtopic.php?t=5542

Answer 5

I found that "exit 0" looks like a good way to deal with this problem.

Usage Example:

NET STOP UnderDevService /Y

exit 0

if the UnderDevService service is not started.

Answer 6

I use VERIFY or VERIFY > nul

Answer 7

If this is a snippet like "Post-build Event" etc., then you'll be fine appending:

(...) || ver > nul

at the end of the last command.

Alternatively

cmd /c "exit /b 0"

is very clean and non-idiomatic -- a reader who knows Windows shell will know what's going on, and what was your intent.

However, if you're in a batch script, you may want to use subrotines, which are a lightweight equivalent of the "child batch script" from akf's answer.

Have a subroutine:

:reset_error
exit /b 0

and then just

call :reset_error

wherever you need it.

Here's a complete example:

@echo off
rem *** main ***

call :raise_error
echo After :raise_error ERRORLEVEL = %ERRORLEVEL%

call :empty
echo After :empty ERRORLEVEL = %ERRORLEVEL%

call :reset_error
echo After :reset_error ERRORLEVEL = %ERRORLEVEL%

:: this is needed at the end of the main body of the script
goto:eof

rem *** subroutines ***

:empty
goto:eof

:raise_error
exit /b 1

:reset_error
exit /b 0

Which outputs:

After :raise_error ERRORLEVEL = 1
After :empty ERRORLEVEL = 1
After :reset_error ERRORLEVEL = 0

As you see - just calling and returning via goto:eof is not enough.

Answer 8

The following works in modern Windows (NT-based) systems that feature cmd.exe:

rem /* This clears `ErrorLevel`; the SPACE can actually be replaced by an
rem    arbitrary sequence of SPACE, TAB, `,`, `;`, `=`, NBSP, VTAB, FF: */
(call )

The SPACE (or more precisely, an arbitrary sequence of one or more standard token separators, which are SPACE (code 0x20), TAB (code 0x09), ,, ;, =, NBSP (code 0xFF), VTAB (code 0x0B) and FF (code 0x0C)) is mandatory; if you omit it the ErrorLevel becomes set instead:

rem // This sets `ErrorLevel` to `1`:
(call)

There is a nice thread on DosTips.com where this technique came up.

---

Here is an alternative method, but which accesses the file system and might therefore be a bit slower:

dir > nul

rem /* Perhaps this is a little faster as a specific file is given rather 
rem    than just the current directory (`.` implicitly) like above: */
dir /B "%ComSpec%" > nul

Answer 9

Here are some other ways to reset the ErrorLevel state, which even work in MS-DOS (at least for version 6.22):

more < nul > nul

rem // The `> nul` part can be omitted in Windows but is needed in MS-DOS to avoid a line-break to be returned:
sort < nul > nul

---

The following methods work in MS-DOS only:

command /? > nul

fc nul nul > nul

keyb > nul

---

For the sake of completeness, this sets the ErrorLevel state to 1, valid for both Windows and MS-DOS:

< nul find ""

Answer 10

After reviewing all of the other answers, I decided to find which way was the most efficient for resetting the ERRORLEVEL. I made a quick script that recorded the time to execute each of these:

"cmd /c "exit /b 0"", "cd .", "ver", "type nul", and "VERIFY"

here is the output:

cmd /v:on /c set ^"q=^"^" & timeit.cmd "cmd /c ^!q^!exit /b 0^!q^!" "cd ." "ver" "type nul" "VERIFY"

cmd /c "exit /b 0" took 0:0:0.02 (0.02s total)

cd . took 0:0:0.00 (0.00s total)

Microsoft Windows [Version 10.0.18362.836]

ver took 0:0:0.00 (0.00s total)

type nul took 0:0:0.00 (0.00s total)

VERIFY is off. VERIFY took 0:0:0.00 (0.00s total)

---

This took 0:0:0.06 (0.06s total)

after reviewing with Measure-Command {command} in Powershell, I found that it only really accepted cd . and cmd /c "exit /b 0" --am I doing something wrong?

I'd recommend either cd . or type nul since neither have a footprint on the output of the console, nor are they slow in any measure.

yeah I'm pretty bored

Answer 11

Add >nul after each command that's likely to fail - this seems to prevent the build from failing.

You can still check the result of the command by examining %errorlevel%.

For example:

findstr "foo" c:\temp.txt>nul & if %errorlevel% EQU 0 (echo found it) else (echo didn't find it)

Answer 12

Tried all solutions above - nothing worked. But found this solution that works for me inside the batch file:

set /A errorlevel=0

(the /A switch defines the supplied value as a numerical expression)

Answer 13

I'm using this:

ping localhost -n 1 >null

Answer 14

I always just used;

set ERRORLEVEL=0

I've been using it for donkey's years.