China DOS Union

Inside (), blank lines and labels (that is, lines starting with : or ::) cannot be used consecutively at the same time


Running the following batch file gives the error “The command syntax is incorrect”; if you remove the blank line or the :: line, it runs normally:

for /l %%i in (1 1 9) do (

echo %%i



::注释

)

pause

Running the following batch file gives the error “The command syntax is incorrect”; if you remove the blank line or the : line, it runs normally:

for /l %%i in (1 1 9) do (

echo %%i



:标签

)

pause

Why is that?

[ Last edited by Hanyeguxing on 2009-9-3 at 02:50 ]

:labels, when placed inside compound code blocks, are inherently meaningless to batch files,
so it should be normal that they can't run;
if they can run, that would instead be a bug in cmd

Originally posted by netbenton at 2009-9-3 02:08:
: Labels, when placed inside a compound block, are inherently meaningless to batch files,
so it's normal if they can't run; if they can run, then that's actually a bug in cmd

But without a blank line, it can run.
It's just that labels and blank lines can't be used inside () at the same time; used separately, either one still works.
Besides, the command-line syntax doesn't specify anything like that either.

[ Last edited by Hanyeguxing on 2009-9-3 at 02:49 ]

It just isn't allowed to be used that way, I guess, so it gives the prompt “The command syntax is incorrect.”

I tried AutoHotkey too, and it can't be used this way either. Code:

{

    msgbox 1

    goto 3

    msgbox 2

    3:

}

After running it, the prompt is:

Error: A label must not point to the end of a block. For loops, use Continue vs. Goto.

I've been working with batch files for ages, but actually there are still a lot of things about cmd preprocessing that I don't dare dig into deeply, just like pointers and memory management in C; subconsciously I always avoid them...

But it's exactly these so-called “bugs” that make cmd more interesting in an invisible way. If used properly, they can achieve a lot of strange functions. Just like malformed directories, we're happy to accept them too.

It really is like that too... can't figure it out