C program to find the length of a string

Given a string str. The task is to find the length of the string.

Examples: 

Input: str = "Geeks"
Output: Length of Str is : 5

Input: str = "GeeksforGeeks"
Output: Length of Str is : 13

In the below program, to find the length of the string str, first the string is taken as input from the user using scanf in , and then the length of Str is calculated using and using method .
Below is the C program to find the length of the string.

Example 1: Using loop to calculate the length of string.

C

// C program to find the length of string
#include <stdio.h>
#include <string.h>

int main()
{
    char Str[1000];
    int i;

    printf("Enter the String: ");
    scanf("%s", Str);

    for (i = 0; Str[i] != '\0'; ++i);

    printf("Length of Str is %d", i);

    return 0;
}

Output

Enter the String: Length of Str is 0

Time Complexity: O(N)
Auxiliary Space: O(1)

Example 2: Using strlen() to find the length of the string.

C

// C program to find the length of
// string using strlen function
#include <stdio.h>
#include <string.h>

int main()
{
    char Str[1000];
    int i;

    printf("Enter the String: ");
    scanf("%s", Str);

    printf("Length of Str is %ld", strlen(Str));

    return 0;
}

Output

Enter the String: Length of Str is 0

Time Complexity: O(1)
Auxiliary Space: O(1)

Example 3: Using sizeof() to find the length of the string.

C

// C program to find the length of
// string using sizeof() function
#include <stdio.h>
#include <string.h>

int main()
{

    printf("Enter the String: ");

    char ss[] = "geeks";

    printf("%s\n", ss);

    // print size after removing null char.
    printf("Length of Str is %ld", sizeof(ss) - 1);

    return 0;
}
// This code is contributed by ksam24000

Output

Enter the String: geeks
Length of Str is 5

Time Complexity: O(1)
Auxiliary Space: O(1)