'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 51 · Accepted Answer · answered Jul 13 '13 at 03:15

51

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

20,187
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score 10 · Answer 2 · edited May 23 '17 at 12:32

10

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

148,593
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712

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;

 }

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

3 Answers3