Batch file and DEL errorlevel 0 issue

Question

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.

Solution 1

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)

Solution 2

Just use rm from UnxUtils (or gow or cygwin). It sets the errorlevel correctly in case of a nonexistent file, or any errors deleting the file.

Solution 3

When using this syntax, instead of this

if errorlevel 0 echo successful

you can use this - because errorlevel 0 is always true.

if not errorlevel 1 echo successful

Comments

[Bob Stein]

Confirm, rm sets errorlevel on a nonexistent file, while del does not.

[Sasha]

Why not just to check if file still exists after deletion attempt?

[aschipfl]

Sure, @Sasha, that is of course also possible; you could write your own answer to show how it could be done, if you want; or do you prefer me to extend mine instead?

[Sasha]

IMHO it's better to have one comprehensive answer. So if you could extend yours it would be perfect.

[lzhh]

2>&1 1> nul might not achieve what you expected; should be 1>nul 2>&1. 2>&1 1>nul redirects STDERR to STDOUT, and what should've been in STDOUT to NUL, i.e. only output STDERR to console.

[aschipfl]

@lxvs, I intentionally used the expression 2>&1 1> nul, because I want to capture STDERR by for /F and ignore STDOUT. The expression 1> nul 2>&1 would suppress both STDOUT and STDERR, so there would be nothing left to capture…

[jifb]

To exchange stdout and stderr, one can use 3>&2 2>&1 1>&3 (even in bash/sh). So the find approach could be del /s /q "%~1" 3>&2 2>&1 1>&3 | find /V "" 3>&2 2>&1 1>&3 & if errorlevel 1 (1> nul ver) else (2> nul set =)