C++ 使用 strlen() 时“未在此范围内声明”
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'not declared in this scope' when using strlen()
提问by Person
I am trying to compile this piece of code but for whatever reason it won't work. Can someone help me? I want to know how to use strlen() properly:
我正在尝试编译这段代码，但无论出于何种原因它都行不通。有人能帮我吗？我想知道如何正确使用 strlen() ：
#include<iostream>
using namespace std;
int main()
{
char buffer[80];
cout << "Enter a string:";
cin >> buffer;
cout << strlen(buffer);
return 0;
}
I've tried using cin.getline(buffer, 80); but I get the same compile error issue.
我试过使用 cin.getline(buffer, 80); 但我遇到了同样的编译错误问题。
My compiler says the error is this
我的编译器说错误是这样的
error: strlen was not declared in this scope
错误：strlen 未在此范围内声明
回答by Rapptz
You forgot to include <cstring>or <string.h>.
您忘记包含<cstring>或<string.h>。
cstringwill give you strlenin the stdnamespace, while string.hwill keep it in the global namespace.
cstring会给你strlen在std命名空间中，同时string.h将它保留在全局命名空间中。
回答by Shafik Yaghmour
You need to include cstringheader for strlen:
您需要包含cstring标题strlen：
#include <cstring>
you could alternatively include string.hand that would put strlenin the global namespace as opposed to stdnamespace. I think it is better practice to use cstringand to drop using using namespace std.
您也可以包含string.h并且将放入strlen全局命名空间而不是std命名空间。我认为使用cstring和放弃使用using namespace std.
