China DOS Union

Brother on the 3rd floor, I'm sorry I didn't understand it originally, but now I've got it. Yours is executable. But I still don't know how to reference the value of a variable. My purpose is like this: First read a line from a.txt, then search in b.txt. If there is no such content in b.txt, add it; if there is, skip it. I realized that my original expression wasn't accurate. I'm sorry.

In addition, you mentioned that you can use a goto loop. I sort of understand the idea, that is, first read a line, then jump to the corresponding program segment accordingly. But now my problem is that I simply don't know how to read a line from a.txt? Using FOR reads until it's done, what should I do?

Thank you in advance!

Yeah, many times it's very important to describe the problem clearly. If you don't know how to describe the steps to solve the problem, just make clear what you want to do.

It's not that I don't understand, but the owner of the post changes too fast.
Hehe, your requirements have changed a lot.
If you don't want to use type, then try findstr + type:
findstr /v /g:b.txt a.txt >>tmp.txt
type tmp.txt >> b.txt
Not tested, theoretically it works, I think this method is more suitable for you than the previous one.

Re 3742668:

It is estimated that the variable in the original poster's mind is not the environment variable, but the replacement variable of for, which is easier to understand.

In addition, your code is indeed skillful, and with a little modification, it can be used to extract the specified lines in the text, which is an algorithm with universal significance.

RE: 3742668

Big brother, thank you! I tested your method, and it turns out to be feasible! Thanks a million!

In addition, I encountered some problems during the test:

1) If both a.txt and b.txt originally have content, the result is consistent with the expected goal when running for the first time, but it is inconsistent when running again. Later I found that tmp.txt was empty the first time, and had content the second time. So I added a line after your code: del tmp.txt

2) If b.txt was originally completely empty, then after running the batch processing, it is still completely empty and does not achieve the expected goal. Of course, I can add an irrelevant line in advance, and then it can achieve my expected goal. But I think that is not the proper way.

Do you have any better solutions?

RE: willsort
Moderator, hello!
You said that with a little modification, you can extract specified lines. Can you make it clear? I'm a newbie and really can't figure out how to achieve this goal?

findstr /v /g:b.txt a.txt >>tmp.txt
type tmp.txt >> b.txt

Please tell me the modified code?

Thanks

Shiver first.

Actually, the things you want to achieve are all in several replies, but you just haven't combined them.

Regarding your question:
1) This is not a problem.
2) Use set /p tmpvar=<b.txt to obtain it, and then use if defined tmpvar to judge whether it is empty.

Finally, shiver again. What willsort said about slightly transforming is not the part of type+findstr, but the previous for. Hehe, it is suggested that you turn over old posts more and run command /?.

Good post, Moderator 3742668 is really enthusiastic!