How to find the length of a string using strlen() in C

Vishnu Damwala

Last updated on Feb 2, 2021 1 min read

A tutorial for finding the length of a string using strlen in C - language

The strlen() function counts the number of characters in a given string and returns the long unsigned integer value.
It is defined in C standard library, within <string.h> header file.

char proudToBeAnIndian[] = "East or West INDIA is best";
strlen(proudToBeAnIndian);

It stops counting when the null character is encounter. Because in C, null character is considered as the end of the string.

Working example

#include <string.h>
#include <stdio.h>

int main()
{
    char planet[] = "Earth", title[] = "MeshWorld";

    printf("\n Using strlen for title without null character: %zu", strlen(title));
    printf("\n Using sizeof for title with null character: %zu", sizeof(title));

    printf("\n Using strlen for planet without null character: %zu", strlen(planet));
    printf("\n Using sizeof for planet with null character: %zu", sizeof(planet));

    return 0;
}

Output

Using strlen for title without null character: 9
Using sizeof for title with null character: 10
Using strlen for planet without null character: 5
Using sizeof for planet with null character: 6

Note that the strlen() function doesn’t count for the null character \0 whereas sizeof() function does.

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