The solutions that search a file for a substring can also search a string, eg. find
or findstr
.
In your case, the easy solution would be to pipe a string into the command instead of supplying a filename eg.
case-sensitive string:
echo "abcdefg" | find "bcd"
ignore case of string:
echo "abcdefg" | find /I "bcd"
IF no match found, you will get a blank line response on CMD and %ERRORLEVEL% set to 1