people will do anything to see a free show.这句子为什么用anything,肯定句不是应用something吗?

anything意为任何事情，可用于否定句中而something意为一些事情，一般不用于否定，但觉不是anything只能用于否定句中，它是任何事的意思，有时需要看句子要表达的意思，判断是用something 还是anything

anything在这里指任何事情，something只是一些事情的意思。如果用something的话，句意就变了啊。

1.PRON-INDEF（用于否定句）任何事物，什么事情You use anything in
statements with negative meaning to indicate in a general way that nothing is
present or that an action or event does not or cannot happen.
We can't do anything...
我们什么都做不了。
Dad sat, not saying anything...
爸爸坐着，一声不吭。
She couldn't see or hear anything at all...
她什么也看不见，什么也听不见。
By the time I get home, I'm too tired to do anything active...
我到家时累得无法动弹。
I couldn't manage anything without you.
没有你，我一事无成。
2.PRON-INDEF（用于疑问句或条件从句）任何事物，任何事情You use anything
in questions and conditional clauses to ask or talk about whether something is
present or happening.
What happened, is anything wrong?...
怎么了，出什么事了吗？
Did you find anything?...
你找到什么了吗？
Is there anything you can do to help?...
你能帮忙做点什么吗？
If there's anything I could do for him, I would.
如果需要我帮他做点什么，我会帮忙的。
3.PRON-INDEF（用于描述所谈论事物的词语前）…的东西，…的事情You can use
anything before words which indicate the kind of thing you are talking
about.
More than anything else, he wanted to become a teacher...
他最想成为一名教师。
Anything that's cheap this year will be even cheaper next year...
今年的便宜货明年会更便宜。
She collects anything that has charm.
她收集一切有特色的东西。
4.PRON-INDEF（用于加强语气）无论什么东西，随便什么事情You use anything
to emphasize a possible thing, event, or situation, when you are saying that it
could be any one of a very large number of things.
He is young, fresh, and ready for anything...
他年轻又富有朝气，什么事都愿意做。
At that point, anything could happen...
那一刻，什么事都可能发生。
He is convinced he just has to say 'please' and he can have anything.
他深信只要说一个“请”字，他就能拥有任何东西。
5.PRON-INDEF（用于强调）多少接近于You use anything in
expressions such as anything near ,anything close to and
anything like to emphasize a statement that you are making.
Doctors have decided the only way he can live anything near a normal life is
to give him an operation...
医生的结论是只有做手术，他才有可能过上基本正常的生活。
Only Cowans played anything close to his true form...
只有考恩斯算是发挥出了正常水平。
Plainer examples of the early period do not fetch anything like these
sums.
早期更为普通的样本卖不到这种价钱。
6.PRON-INDEF（限定范围内的）任何一点When you do not want to be exact,
you use anything to talk about a particular range of things or
quantities.
Factory farming has turned the cow into a milk machine, producing anything
from 25 to 40 litres of milk per day...
集约饲养把奶牛变成了生产牛奶的机器，每天差不多要挤出25升到40升的牛奶。
Fights with his father lasted anything between fifteen minutes and an
hour.
和他父亲争吵了大约15分钟到一个小时。
Usage
Note:
Anything is mainly used in questions and negative sentences. You use
not anything instead of something in negative sentences. There
isn't anything here.
anything主要用于疑问句和否定句。否定句中用not anything代替something，如：There isn't anything
here（这儿什么也没有）。
7.PHRASE（用于形容词后表示强调）非常，十分You use as anything
after an adjective to emphasize a quality that someone has.
He used to be as smart as anything...
他过去聪明绝顶。
She opened the door and jumped out, quick as anything.
她打开门，飞快地跳了出来。
8.PHRASE单单除…之外；根本不；远非You use anything but in
expressions such as anything but quiet and anything but attractive
to emphasize that something is not the case.
I will be anything but quiet on Saturday night!...
星期六的晚上我根本静不下心来！
There's no evidence that he told anyone to say anything but the truth...
并无证据表明他让什么人隐瞒真相。
The Los Angeles police chief was not always so insulated from politicians;
anything but.
洛杉矶警察局局长并不总是如此疏远政客，根本不会。
9.PHRASE决不You can say
that you would not do something for anything to emphasize that you
definitely would not want to do or be a particular thing.
I wouldn't want to move for anything in the world...
就是天塌了我也不搬走。
I wouldn't have missed this summer in England for anything...
我本来说什么也不会错过在英格兰的这个夏季的。
I wouldn't be without Matthew for anything.
我决不会离开马修。
10.PHRASE（尤用于否定句后，对所说之事进行补充说明）甚至正相反，甚至还不如说You use
if anything, especially after a negative statement, to introduce a
statement that adds to what you have just said.
I never had to clean up after him. If anything, he did most of the
cleaning.
我从来不用跟在他后面打扫卫生。恰恰相反，他包揽了大部分的清洁工作。
11.PHRASE或其他什么的；诸如此类You can add or anything to
the end of a clause or sentence in order to refer vaguely to other things that
are or may be similar to what has just been mentioned.
Listen, if you talk to him or anything make sure you let us know, will
you...
听着，如果你和他说话或什么的，一定要让我们知道，好吗？
He didn't cry or scream or anything.
这里应该是指第四种，表示强调

是的，这里anything表示任何事情，这时候那个“肯定句用some, 否定句疑问句用any”的规则就不管用了

您要看句子要表达的意思.
这句话要表达的是：为了看到免费的表演,人们将会做出任何事情.（字面理解）
所以,要用 anything
如果在这里用something,句子的意思就变了,是人们将会做一些特定的事情,这些事情是可以预料的,是一定发生的.
希望能够帮助到您.