Batch file and DEL errorlevel 0 issue
The batch has to remove files and directories from specific locations and output success or stdout/stderr messages to a new .txt file. I have created the most of the script and it performs exactly as it should, except when the deletion is successful it moves forward to the next line rather than echo a 'successful' message on the log.
echo Basic Deletion Batch Script > results.txt
@echo off
call :filelog >> results.txt 2>&1
notepad results.txt
exit /b
:filelog
call :delete new.txt
call :delete newer.txt
call :delete newest.txt
call :remove c:\NoSuchDirectory
GOTO :EOF
:delete
echo deleting %1
del /f /q c:\Users\newuser\Desktop\%1
if errorlevel 0 echo succesful
GOTO :EOF
:remove
echo deleting directory %1
rmdir /q /s %1
GOTO :EOF
For some reason I can't find the syntax for if del succeeds echo 'successful'. In the above example if I remove the line
if errorlevel 0 echo successful
Everything works fine, but no success message. With this line left in it echoes success for every line.
Answer
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)