China DOS Union

Because I'm a beginner, I'm not very clear about the restrictions on the variable names in SET [variable=[string]]. After checking the help with set /?, I found this sentence: "The SET command does not allow variable names to contain equal signs."

At first, I didn't pay attention to this sentence. When doing exercises, I found a problem. I tested in the command-line interpreter:

1. C:\Documents and Settings\wang>set var =look
2. C:\Documents and Settings\wang>set name=%var:l=b%
3. C:\Documents and Settings\wang>set name
4. name=%var:l=b%

I was very puzzled why name wasn't replaced by var. Then I used set var and found:

5. C:\Documents and Settings\wang>set var
6. var =look

At this time, I felt a little problem (because I didn't find the problem yet). Then I used echo %var% and found:

7. C:\Documents and Settings\wang>echo %var%
8. %var%

Suddenly, I felt that var was problematic. Then I used echo %var %:

9. C:\Documents and Settings\wang>echo %var %
10. look

At this time, I suddenly understood that when I set var =look in the first sentence, it was setting var (with a space), not var. So after the second sentence name=%var:l=b%, the value of name was =%var:l=b%. My original intention was to replace look with book and assign it to name.

In the 5th and 6th sentences, the reason why I could use set var to see the value of var was because of another help sentence of SET:
You can use only one variable to activate the SET command. If there is no equal sign or value, all prefix-matched variable values of the SET command will be displayed.
For example:
SET P
will display all variables starting with the letter P

In this way, because I didn't pay attention to the space problem before, I didn't pay much attention here.
It wasn't until the 7th and 8th sentences that I felt there might be a space problem. Finally, I found that it was indeed this problem.
Because when I used other languages to write programs before, I always used to add a space after the variable name, which was convenient for reading. But in DOS's set, a variable with a space and one without a space are two different variables.
After finding this problem, I thought of the help sentence at the beginning. Then can other special symbols be used in variable names except =?
I simply tested and found the following problems:
1. Special characters like & cannot be used in variable names (for example, set po6&9$%^155 =123). If used, it will be considered as the connection of two commands and an error will be reported (this is just my test, I don't know about others).
2. Paired quotation marks "" cannot be used in variable names (for example, set hha"#%45" rg =456). If used, an error will also occur.
3. If there is ^ in the variable name, no error will be reported, but ^ will be filtered out.
I also tested some other characters, and there seemed to be no problems. For example, I can set:
set [{!}~e ge w4%t %] sd =6
In this way, the value of the variable [{!}~e ge w4%t %] sd is 6.
In this way, it's not that only = cannot be used in variable names, and variables ending with spaces are easily confused with non-space-ending variables of the same name by people.

The above are just some problems I found when doing exercises. I hope experts can give theoretical explanations. Thank you.

When setting a value for a variable, besides the space between the set command itself and the variable name, spaces are not ignored by default. This is both an advantage and a disadvantage.

E:\>set cn dos = hey, everybody

E:\>set cn
cn dos = hey, everybody

E:\>echo


E:\>

I also tested some other characters, and there doesn't seem to be any problems. For example, you can set the following
set sd =6
In this way, the value of the variable sd is 6.

I don't understand why you set the variable name like this. It's like setting a variable name as lakjsdlfjlsjfhkshfs in other languages, which is meaningless. If it's purely for researching the "features" of cmd, that's another story.

Turn off these default shares

Re lxmxn
The reason I set a meaningless name is purely to test whether such a variable name can be set. If I set set I love my gf=, would it have a little practical meaning? Of course, the spaces can also be completely removed, just talking casually.
In addition, personally, I think that the disadvantage is that the variable name after set does not ignore spaces. As for the advantages you mentioned, can you explain? Thank you.

Re ashu791
I don't understand what you mean by "closing these default shares"?

[ Last edited by newsuper on 2000-10-19 at 08:01 ]