China DOS Union

In batch files I often see statements like this, starting with an echo, and ending with “>nul 2>nul”.

nul is a null device, so what is nul 2?
If you want the output not to be shown, wouldn’t just >nul be enough? Why is there also nul 2 in front?

Thanks for all your replies

It’s not nul 2, but 2> nul, which means the error messages are also sent to the null device, that is, even the error messages are not shown. Under normal circumstances, a command outputs its results to standard output, and standard output is represented by 1, so the >nul you typed is actually 1>nul (note that there cannot be a space between 1 and &gt. But during the execution of some commands, error messages are displayed. >nul cannot hide these error messages, because these error messages do not belong to standard output, but to standard error output. Standard error output is represented by 2, so 2> nul means not to display error messages. For example, take the dir command (the bold part indicates the prompt and command line, and what follows is the command’s execution result):\XYF\System\dos>dir abcd
Volume in drive D is HDAL2_WORK
Volume Serial Number is 58BA-2D5D Directory of D:\XYF\System\dosFile Not FoundD:\XYF\System\dos>dir abcd > nul
File Not FoundD:\XYF\System\dos>dir abcd 1> nul
File Not FoundD:\XYF\System\dos>dir abcd 1> nul 2>nulD:\XYF\System\dos>dir abcd >nul 2>nulD:\XYF\System\dos>dir abcd 2>nul
Volume in drive D is HDAL2_WORK
Volume Serial Number is 58BA-2D5D Directory of D:\XYF\System\dos

DVBBS forums really suck, I just absolutely can’t make it bold.

I really am very grateful to climbing～～～～～～～～～～～～～～～～echo Thx climbing very much 1>nul 2>nul

Come on, if you echo it like that, then there’s no thanks at all, geez~~~

Haha, you two are really humorous! So NUL has this kind of trick to it too.

The following is quoted from Climbing’s post at 2005-3-11 18:34:30:

Come on, if you echo it like that, then there’s no thanks at all, geez~~~

Sorry about that. It was just a way of expressing my feelings. Just take it as me not saying thanks out loud; in fact I’m already very grateful in my heart.

^_^ Nice

The following is quoted from Climbing’s post at 2005-3-11 13:01:59:

It’s not nul 2, but 2> nul, which means the error messages are also sent to the null device, that is, even the error messages are not shown.
Under normal circumstances, a command outputs its results to standard output, and standard output is represented by 1, so the >nul you typed is actually 1>nul (note that there cannot be a space between 1 and &gt. But during the execution of some commands, error messages are displayed. >nul cannot hide these error messages, because these error messages do not belong to standard output, but to standard error output. Standard error output is represented by 2, so 2> nul means not to display error messages.
For example, take the dir command:
D:\XYF\System\dos>dir abcd
Volume in drive D is HDAL2_WORK
Volume Serial Number is 58BA-2D5D
Directory of D:\XYF\System\dos
File Not Found
D:\XYF\System\dos>dir abcd > nul
File Not Found
D:\XYF\System\dos>dir abcd 1> nul
File Not Found
D:\XYF\System\dos>dir abcd 1> nul 2>nul
D:\XYF\System\dos>dir abcd >nul 2>nul
D:\XYF\System\dos>dir abcd 2>nul
Volume in drive D is HDAL2_WORK
Volume Serial Number is 58BA-2D5D
Directory of D:\XYF\System\dos

Today I learned some good stuff again