C Programming: Find the length of a string

Last update on October 24 2025 12:11:11 (UTC/GMT +8 hours)

2. String Length Without Library

Write a program in C to find the length of a string without using library functions.

Sample Solution:

C Code:

#include <stdio.h>
#include <stdlib.h>

int main() {
    char str[100]; /* Declares a string of size 100 */
    int l = 0; // Initialize a variable to store the length of the string
	
    printf("\n\nFind the length of a string :\n"); // Display information about the task
    printf("---------------------------------\n"); 	
    printf("Input the string : ");

    // Read a string from the standard input (keyboard) using fgets()
    fgets(str, sizeof str, stdin);

    // Loop to calculate the length of the string
    while (str[l] != '\0') {
        l++; // Increment the length counter until the null terminator '\0' is encountered
    }

    printf("Length of the string is : %d\n\n", l - 1); // Display the length of the string
	
	return 0; // Return 0 to indicate successful execution of the program
}

Output:

Find the length of a string :                                                                                 
---------------------------------                                                                             
Input the string : w3resource.com                                                                             
Length of the string is : 15

Flowchart:

Flowchart: Find the length of a string.

For more Practice: Solve these Related Problems:

Write a C program to compute the length of a string recursively without using any library functions.
Write a C program to determine the length of a string using pointer arithmetic without looping explicitly.
Write a C program to calculate a string’s length by iterating over its characters until the null terminator is reached.
Write a C program to read a string from a file and calculate its length manually without library support.

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