What is the strlen() Function in C++

C++ strlen() is a built-in function used to calculate the length of the string. The method returns the length of the given C-string and is defined under the string.h header file. The strlen() takes a null-terminated byte string str as its argument and returns its length. The length does not include a null character.

Syntax

int strlen(const char *str_var);

Here, str_var is the string variable we have to find the length.

Parameters

It takes one parameter, a pointer that points to the null-terminated byte string. A null character terminates the string. If a null character does not terminate it, the behavior is undefined.

Return Value

It returns an integer giving the length of the passed string.

Example 1

#include <iostream>
#include <string.h>

using namespace std;

int main()
{
  char k[] = "hello world";
  char m[] = "I am the best\n";
  char n[] = "a";
  char o[] = "123";
  int f, i, g, h;
  f = strlen(k);
  i = strlen(m);
  g = strlen(n);
  h = strlen(o);
  cout << "String: " << k << endl;
  cout << "Length: " << strlen(k) << endl;
  cout << "String: " << m << endl;
  cout << "Length: " << strlen(m) << endl;
  cout << "String: " << n << endl;
  cout << "Length: " << strlen(n) << endl;
  cout << "String: " << o << endl;
  cout << "Length: " << strlen(o) << endl;
}

Output

String: hello world
Length: 11
String: I am the best
 
Length: 14
String: a
Length: 1
String: 123
Length: 3

Example 2

#include <iostream>
#include <string.h>

using namespace std;

int main()
{
  char a[] = "Hello I am a geek!";
  char b[] = "I love AppDividend!";
  if (strlen(a) == strlen(b))
  {
    cout << "Length of both the strings are equal";
  }
  else
  {
    cout << "Length of the both the strings are not equal";
  }
}