Find String Length Without strlen() in C | Simple Program

Finding the length of a string is a fundamental operation in programming. While many programming languages provide built-in functions like strlen() in C, there are alternative methods to calculate the length manually. In this article, we’ll explore two approaches to find the length of a string without using the strlen() function.

Table of Contents

1. Introduction
2. Why Avoid strlen()?
3. Methods to Find the Length of a String
   • Using a Character-by-Character Scan
   • Using Pointers
4. C Programs for Each Method
5. Conclusion

Introduction

Strings are an essential data type in programming. Understanding how to manipulate and analyze strings without relying on built-in functions like strlen() can deepen your understanding of how strings work at a low level.

1. Why Avoid strlen()?

There are several scenarios where avoiding strlen() might be beneficial:

• Educational: Understanding how strlen() works internally.
• Custom Implementation: Creating a solution for systems that lack built-in libraries.
• Performance Optimization: Tailoring string operations to specific requirements.

2. Methods to Find the Length of a String

Method 1: Using a Character-by-Character Scan

In this method, the string is traversed one character at a time until the null character (\0) is encountered. The count of characters before the null character represents the length of the string.

Method 2: Using Pointers

This method uses pointers to traverse the string. The pointer starts at the beginning of the string and increments until the null character (\0) is reached. The difference between the final pointer position and the initial position gives the string’s length.

3. C Programs for Each Method

Program 1: Using a Character-by-Character Scan

#include <stdio.h>

// Function to find the length of a string
int findLength(char str[]) {
    int length = 0;
    while (str[length] != '\0') {
        length++;
    }
    return length;
}

int main() {
    char str[100];

    // Input string from user
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);

    // Remove newline character if present
    str[strcspn(str, "\n")] = '\0';

    // Find and print the length of the string
    printf("Length of the string: %d\n", findLength(str));

    return 0;
}

Program 2: Using Pointers

#include <stdio.h>

// Function to find the length of a string using pointers
int findLengthUsingPointers(char *str) {
    char *ptr = str;
    while (*ptr != '\0') {
        ptr++;
    }
    return ptr - str;
}

int main() {
    char str[100];

    // Input string from user
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);

    // Remove newline character if present
    str[strcspn(str, "\n")] = '\0';

    // Find and print the length of the string
    printf("Length of the string: %d\n", findLengthUsingPointers(str));

    return 0;
}

Conclusion

By avoiding the strlen() function, you can better understand how strings are stored and processed in memory. The character-by-character scan is straightforward, while the pointer method is more advanced and efficient for certain scenarios.