What is the proper way to test is variable is empty in a batch file, If NOT "%1" == "" GOTO SomeLabel, fails if %1 has quotes.

Question

I need to test if a variable is set or not. I've tried several techniques but they seem to fail whenever %1 is surrounded by quotes such as the case when %1 = "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.

According to this site. These are the support IF syntax types. So, I don't see a way to do it.

IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command

Answer 1

Use parentheses instead of quotes:

IF (%1) == () GOTO MyLabel

Answer 2

I usually use this:

IF "%1."=="." GOTO MyLabel

If %1 is empty, the IF will compare "." to "." which will evaluate to true.

Answer 3

You can use:

IF "%~1" == "" GOTO MyLabel

to strip the outer set of quotes.

Answer 4

From IF /?:

If Command Extensions are enabled IF changes as follows:

IF [/I] string1 compare-op string2 command
IF CMDEXTVERSION number command
IF DEFINED variable command

......

The DEFINED conditional works just like EXISTS except it takes an environment variable name and returns true if the environment variable is defined.