'not declared in this scope' when using strlen()

Question

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:

 #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.

My compiler says the error is this

error: strlen was not declared in this scope

my compiler says this:error: âstrlenâ was not declared in this scope — Person, Jul 13 '13 at 03:15
check out this [example](http://www.cplusplus.com/reference/cstring/strlen/) — lambda, Jul 13 '13 at 03:17
If you want to write C++ then you should be using `std::string`. — Ed S., Jul 13 '13 at 03:26

score 55 · Accepted Answer · answered Jul 13 '13 at 03:15

55

You forgot to include <cstring> or <string.h>.

cstring will give you strlen in the std namespace, while string.h will keep it in the global namespace.

answered Jul 13 '13 at 03:15

Rapptz

20,807
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score 11 · Answer 2 · edited May 23 '17 at 12:32

11

You need to include cstring header for strlen:

 #include <cstring>

you could alternatively include string.h and that would put strlen in the global namespace as opposed to std namespace. I think it is better practice to use cstring and to drop using using namespace std.

edited May 23 '17 at 12:32

Community

1
1

answered Jul 13 '13 at 03:14

Shafik Yaghmour

154,301
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score 0 · Answer 3 · answered Dec 22 '20 at 17:19

You can include <cstring>, then you won't get any errors.

code

#include<iostream>
#include<cstring>
 using namespace std;

 int main()
 {
    char buffer[80];

    cout << "Enter a string:";
    cin >> buffer;
    cout << strlen(buffer);

    return 0;

 }

score -1 · Answer 4 · answered Apr 26 '23 at 06:35

You can use string.h header file in C++ but it is generally not recommended. In C++, the string class is part of the standard library and provides more functionality for manipulating strings than the functions declared in string.h.

The string class provides features like dynamic memory allocation, overloaded operators, iterators, and more, making it easier to work with strings in C++. Using string.h in C++ may limit the benefits of these features and make the code harder to read and maintain.

To use the string class in C++, you can include the header file. This header file declares the std::string class and associated functions and provides a more modern and efficient way of working with strings in C++.

'not declared in this scope' when using strlen()

4 Answers4