del and ErrorLevel?
The del command does not set the ErrorLevel as long as the given arguments are valid, it even resets the ErrorLevel to 0 in such cases (at least for Windows 7).
del modifies the ErrorLevel only in case an invalid switch is provided (del /X sets ErrorLevel to 1), no arguments are specified at all (del sets ErrorLevel to 1 too), or an incorrect file path is given (del : sets ErrorLevel to 123), at least for Windows 7.
Possible Work-Around
A possible work-around is to capture the STDERR output of del, because in case of deletion errors, the related messages (Could Not Find [...], Access is denied., The process cannot access the file because it is being used by another process.) are written there. Such might look like:
for /F "tokens=*" %%# in ('del /F /Q "\path\to\the\file_s.txt" 2^>^&1 1^> nul') do (2> nul set =)
To use the code in command prompt directly rather than in a batch file, write %# instead of %%#.
If you do not want to delete read-only files, remove /F from the del command line;
if you do want prompts (in case wildcards ? and/or * are present in the file path), remove /Q.
Explanation of Code
This executes the command line del /F /Q "\path\to\the\file_s.txt". By the part 2>&1 1> nul, the command output at STDOUT will be dismissed, and its STDERR output will be redirected so that for /F receives it.
If the deletion was successful, del does not generate a STDERR output, hence the for /F loop does not iterate, because there is nothing to parse. Notice that ErrorLevel will not be reset in that case, its value remains unchanged.
If for /F recieves any STDERR output from the del command line, the command in the loop body is executed, which is set =; this is an invalid syntax, therefore set sets the ErrorLevel to 1. The 2> nul portion avoids the message The syntax of the command is incorrect. to be displayed.
To set the ErrorLevel explicitly you could also use cmd /C exit /B 1. Perhaps this line is more legible. For sure it is more flexible because you can state any (signed 32-bit) number, including 0 to clear it (omitting the number clears it as well). It might be a bit worse in terms of performance though.
Application Example
The following batch file demonstrates how the above described work-around could be applied:
:DELETE
echo Deleting "%~1"...
rem this line resets ErrorLevel initially:
cmd /C exit /B
rem this line constitutes the work-around:
for /F "tokens=*" %%# in ('del /F /Q "C:\Users\newuser\Desktop\%~1" 2^>^&1 1^> nul') do (2> nul set =)
rem this is the corrected ErrorLevel query:
if not ErrorLevel 1 echo Deleted "%~1" succesfully.
goto :EOF
Presetting ErrorLevel
Besides the above mentioned command cmd /C exit /B, you can also use > nul ver to reset the ErrorLevel. This can be combined with the for /F loop work-around like this:
> nul ver & for /F "tokens=*" %%# in ('del /F /Q "\path\to\the\file_s.txt" 2^>^&1 1^> nul') do (2> nul set =)
Alternative Method Without for /F
Instead of using for /F to capture the STDERR output of del, the find command could also be used like find /V "", which returns an ErrorLevel of 1 if an empty string comes in and 0 otherwise:
del "\path\to\the\file_s.ext" 2>&1 1> nul | find /V "" 1> nul 2>&1
However, this would return an ErrorLevel of 1 in case the deletion has been successful and 0 if not. To reverse that behaviour, an if/else clause could be appended like this:
del "\path\to\the\file_s.ext" 2>&1 1> nul | find /V "" 1> nul 2>&1 & if ErrorLevel 1 (1> nul ver) else (2> nul set =)
Different Approach: Checking File for Existence After del
A completely different approach is to check the file for existence after having tried to delete it (thanks to user Sasha for the hint!), like this, for example:
del /F /Q "\path\to\the\file_s.txt" 1> nul 2>&1
if exist "\path\to\the\file_s.txt" (2> nul set =) else (1> nul ver)