How do you suppress environment variable expansion

问题:

This is a simplified example with modified variable names of what I want to do. Also for simplicity sake, I am showing the command line version rather than the bat file version.

I am doing the following.

> echo %foo%

%foo%

However, if foo is a valid environment variable, I do not get desired output (%foo%) due to environment variable expansion.

> set foo=bar
> echo %foo%
> echo %%foo%%

bar
%bar%

Now, I have a hack to do (following example) this but I was wondering if there is a cleaner way to either output a % character or to suppress environment variable expansion.

> set foo=bar
> set percent=%
> echo %percent%foo%percent%

%foo%

Also, if the required solution is different in a bat file (like %% rather than % or %1% rather than %1) please let me know.

My actual use case is in a bat file with SETX to set global environment variables that rely on another environment variable to be expanded within them but I'm curious as to how to expand in either DOS or cmd.

回答1:

in a batch file, echo %%foo%% will generate %foo%.

c:\01Temp>type foo.bat
@echo %%foo%%

c:\01Temp>foo
%foo%

c:\01Temp>

回答2:

Within a batch file, use two %%s, e.g.:

set foo=1
echo %%foo%%

...echoes "%foo%", not "1". I'm not aware of a way to disable it in immediate mode (e.g., not in a batch file).