C strcmp() Function

The strcmp() function in C is a standard library function that compares two strings. It is part of the C standard library (string.h). This function is useful for comparing the lexicographical order of two strings.

Table of Contents

1. Introduction
2. strcmp() Function Syntax
3. Understanding strcmp() Function
4. Examples
   • Comparing Two Identical Strings
   • Comparing Different Strings
5. Real-World Use Case
6. Conclusion

Introduction

The strcmp() function compares two null-terminated strings lexicographically. It returns an integer less than, equal to, or greater than zero if the first string is found to be less than, equal to, or greater than the second string, respectively.

strcmp() Function Syntax

The syntax for the strcmp() function is as follows:

int strcmp(const char *str1, const char *str2);

Parameters:

• str1: A pointer to the first null-terminated string to be compared.
• str2: A pointer to the second null-terminated string to be compared.

Returns:

• The function returns an integer:
  • Less than zero if str1 is less than str2.
  • Zero if str1 is equal to str2.
  • Greater than zero if str1 is greater than str2.

Understanding strcmp() Function

The strcmp() function performs a lexicographical comparison of the two strings, which means it compares the strings character by character using the ASCII values of the characters. The comparison stops when a difference is found or the end of the strings is reached.

Examples

Comparing Two Identical Strings

To demonstrate how to use strcmp() to compare two identical strings, we will write a simple program.

Example

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

int main() {
    char str1[] = "Hello, World!";
    char str2[] = "Hello, World!";

    // Compare the strings using strcmp
    int result = strcmp(str1, str2);

    // Print the result
    printf("Comparison result: %d\n", result);

    return 0;
}

Output:

Comparison result: 0

Comparing Different Strings

This example shows how to use strcmp() to compare different strings.

Example

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

int main() {
    char str1[] = "Hello, World!";
    char str2[] = "Hello, Ramesh!";

    // Compare the strings using strcmp
    int result = strcmp(str1, str2);

    // Print the result
    if (result < 0) {
        printf("\"%s\" is less than \"%s\"\n", str1, str2);
    } else if (result > 0) {
        printf("\"%s\" is greater than \"%s\"\n", str1, str2);
    } else {
        printf("\"%s\" is equal to \"%s\"\n", str1, str2);
    }

    return 0;
}

Output:

"Hello, World!" is less than "Hello, Ramesh!"

Real-World Use Case

Sorting an Array of Strings

In real-world applications, the strcmp() function can be used to sort an array of strings lexicographically.

Example: Sorting an Array of Strings

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

void sortStrings(char arr[][20], int n) {
    char temp[20];
    for (int i = 0; i < n - 1; i++) {
        for (int j = i + 1; j < n; j++) {
            if (strcmp(arr[i], arr[j]) > 0) {
                strcpy(temp, arr[i]);
                strcpy(arr[i], arr[j]);
                strcpy(arr[j], temp);
            }
        }
    }
}

int main() {
    char arr[][20] = {"Ramesh", "Suresh", "Mahesh", "Naresh", "Kalpesh"};
    int n = sizeof(arr) / sizeof(arr[0]);

    // Sort the array of strings
    sortStrings(arr, n);

    // Print the sorted array
    printf("Sorted array of strings:\n");
    for (int i = 0; i < n; i++) {
        printf("%s\n", arr[i]);
    }

    return 0;
}

Output:

Sorted array of strings:
Kalpesh
Mahesh
Naresh
Ramesh
Suresh

Conclusion

The strcmp() function is used for comparing strings in C. By understanding and using this function correctly, you can efficiently compare and sort strings in your programs. Always ensure that the strings are null-terminated to prevent undefined behavior. This function is particularly useful for tasks that involve sorting, searching, and lexicographical comparisons of strings.