ERRORLEVEL is not %ERRORLEVEL%

最新推荐文章于 2024-05-07 16:30:12 发布

lijin912

最新推荐文章于 2024-05-07 16:30:12 发布

阅读量960

点赞数

分类专栏： Batch/NSIS 文章标签： command behavior include file types c

Batch/NSIS 专栏收录该内容

0 篇文章

订阅专栏

本文解析了CMD命令解释器中ERRORLEVEL的概念及其与名为ERRORLEVEL的环境变量之间的区别。ERRORLEVEL用于记录最近运行程序的退出代码，可通过IF ERRORLEVEL命令进行测试。而设置的ERRORLEVEL环境变量不会影响命令解释器内部的ERRORLEVEL状态。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

转帖自http://blogs.msdn.com/oldnewthing/archive/2008/09/26/8965755.aspx

ERRORLEVEL is not %ERRORLEVEL%

The command interpreter cmd.exe has a concept known as the error level, which is the exit code of the program most recently run. You can test the error level with the IF ERRORLEVEL command:

IF ERRORLEVEL 1 ECHO error level is 1 or more

<sidebar>
The IF ERRORLEVEL n test succeeds if the error level is n or more. This was presumably because there were programs that expressed different degrees of failure with higher and higher exit codes. For example, the diff program has three exit codes: 0 means the files are the same; 1 means the files are different; 2 means that something terrible happened. There are also programs that use an exit code of zero to mean success and anything else to mean failure.
</sidebar>

In addition to this internal state, you can, if you wish, create an environment variable with the name ERRORLEVEL, in the same way that you can create an environment variable called FRED. But, as with FRED, that variable won't have any effect on the error level.

rem this next command sets the error level to zero
CMD /C EXIT 0
set ERRORLEVEL=1
if ERRORLEVEL 1 echo Does this print?

The message is not printed because the ERRORLEVEL environment variable has no effect on the error level. It's just a variable whose name happens to coincide with a command processor concept.

set BANKBALANCE=$1,000,000.00

"Hey, when I tried to withdraw the money, I got an insufficient funds error. What am I doing wrong?"

Now, it does happen to be the case that if command extensions are enabled and you say %ERRORLEVEL%, then the command processor first looks for an environment variable called ERRORLEVEL, and if it can't find one, then it replaces %ERRORLEVEL% with the current value of the internal error level value. It's a fallback step, in the same way that your neighbor is a fallback delivery location if you aren't home. If you file a change-of-address form for yourself, that doesn't affect packages sent to your neighbor.

The same behavior can be seen with %CD%: If you did not explicitly set an environment variable called CD, then %CD% expands to the command processor's current directory. But you can't change directories by saying set CD=C:/Windows.

I can think of a few reasons why this feature may have been added.

So you can include the error level in a log file:
ECHO error level is %ERRORLEVEL%>logfile
So you can perform other types of tests against the error level, for example, to perform an equality test:
IF %ERRORLEVEL% EQU 1 echo Different!

But I'm digressing. My point for today is that the error level is not the same as the ERRORLEVEL environment variable.