I need to test if a variable is set or not. I've tried several techniques but they seem to fail whenever
"c:\some path with spaces"
IF NOT %1 GOTO MyLabel // This is invalid syntax
IF "%1" == "" GOTO MyLabel // Works unless %1 has double quotes which fatally kills bat execution
IF %1 == GOTO MyLabel // Gives an unexpected GOTO error.
IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command
Use brackets instead of quotes:
IF [%1] ==  GOTO MyLabel
Note: The original answer was:
IF (%1) == () GOTO MyLabel
@jeb pointed out this was insecure, and @Synetech suggested an alternative so I revised the answer.