findstr exit codes/errorlevel

Question

I have a program that is using findstr, and when the string is found the errorlevel returns 0 and when the string is not found the errorlevel returns 1. Alright, that's fine I can deal with that.

Where the issue lies is I cannot find any official documentation on what each errorlevel means for findstr. I need to know if anything else for findstr could ever return an errorlevel of 1, or if it only returns 1 when the string is not found.

Links to 'official' documentation are preferred, if there are any, but any input would be greatly appreciated.

Thanks in advance!

Answer 1

http://ss64.com/nt/findstr.html says:

FINDSTR will set %ERRORLEVEL% as follows:

0 (False) a match is found in at least one line of at least one file.
1 (True) if a match is not found in any line of any file, (or if the file is not found at all).
2 Wrong syntax 
An invalid switch will only print an error message in error stream.