What is the easiest way to reset ERRORLEVEL to zero? - windows

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

I'm using this:
ping localhost -n 1 >null

Answer 13

I always just used;
set ERRORLEVEL=0
I've been using it for donkey's years.