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Compare String

Introduction

The strcmp function is part of the standard C library and is used to compare two strings. This function determines the lexicographical order of the given strings.

Syntax

#include <string.h>

int strcmp(char str1[], char str2[]);

  • Parameters:

    • str1: Array representing the first string.
    • str2: Array representing the second string.

  • Return Value:

    • Returns a value less than 0 if str1 is less than str2.
    • Returns 0 if str1 is equal to str2.
    • Returns a value greater than 0 if str1 is greater than str2.

Explanation

The strcmp function compares two strings character by character in a lexicographical manner. The comparison stops when a difference is found or when the end of one of the strings is reached.

Example Usage

Below is a simple C program demonstrating the use of strcmp:

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

int main() {
    char str1[] = "Geeks";
    char str2[] = "Geeks";
    char str3[] = "GEEKS";

    // Comparing str1 and str2
    int result = strcmp(str1, str2);
    if (result == 0) {
        printf("str1 and str2 are equal.\n");
    } else {
        printf("str1 and str2 are different.\n");
    }

    // Comparing str1 and str3
    result = strcmp(str1, str3);
    if (result == 0) {
        printf("str1 and str3 are equal.\n");
    } else {
        printf("str1 and str3 are different.\n");
    }

    return 0;
}

Expected Output:

str1 and str2 are equal.
str1 and str3 are different.

In the example above, strcmp(str1, str2) returns 0 because both strings are identical. However, strcmp(str1, str3) returns a nonzero value because of the difference in letter casing.

Using strcmp in Searching

The strcmp function can also be used in searching within an array of strings. Below is an example demonstrating how to search for a string in an array using strcmp:

#include <stdio.h>
#include <string.h>
#define SIZE 5

int main() {
    char names[SIZE][20] = {"Alice", "Bob", "Charlie", "David", "Eve"};
    char search[20];
    int found = 0;

    printf("Enter a name to search: ");
    scanf("%s", search);

    for (int i = 0; i < SIZE; i++) {
        if (strcmp(names[i], search) == 0) {
            printf("%s found at position %d\n", search, i + 1);
            found = 1;
            break;
        }
    }

    if (!found) {
        printf("%s not found in the list.\n", search);
    }
    
    return 0;
}

Expected Output:

Enter a name to search: Bob
Bob found at position 2

This program takes user input for a name and searches for it in the predefined list using strcmp.

Important Notes

  • The strcmp function is case-sensitive. To perform a case-insensitive comparison, you can use strcasecmp (available on some platforms) or convert both strings to lowercase or uppercase before comparing.
  • Ensure both string arrays are valid and contain null-terminated strings ('\0') to avoid undefined behavior.
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