C Library - strcmp() function

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The C Library strcmp() function is used to compare two strings. It checks each character in the string one by one until it finds a difference or reaches the end of the one string. Additionally, the strings comparison is based on ASCII values.

Syntax

Following is the syntax of the C library strcmp() function −

strcmp(const char *str_1, const char *str_2)

Parameters

This function accepts the following parameters−

• str_1 − This parameter define the first string to be compared.

• str_2 − This is the second string to compare with first/previous string.

Return Value

This function returns the integer value which is −

• Zero, if the string are equal.

• Negative, if the first string is less than second string lexicographically.

• Positive, if the first string is greater than second string lexicographically.

Example 1

In this example, we demonstrate the usage of string characters comparison using strcmp() function.

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

int main() {

   char str1[] = "abcd", str2[] = "abcd";
   int res;

   // Compare the strings str1 and str2
   res = strcmp(str1, str2);
   printf("strcmp(str1, str2) = %d\n", res);
   return 0;
}

Output

The above code produces the following result−

strcmp(str1, str3) = 0

Example 2

To check whether the given strings are case-sensitive or not using strcmp() and conditional statement.

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

int main() 
{
   char str1[] = "Tutorials";
   char str2[] = "tutorials";
   // Compare the strings
   int result = strcmp(str1, str2);
   
   if (result == 0) {
       printf("Strings are equal(case-sensitive)\n");
   } 
   else {
        printf("Strings are not equal(case-insensitive).\n");   
   }
return 0;
}

Output

On execution of above code, we get the following result −

Strings are not equal(case-insensitive).

Example 3

Below the example create the strings of different size and check its comparison using strcmp().

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

int main() 
{
   char str_1[] = "BOOK";
   char str_2[] = "UNIVERSITY";

   int res = strcmp(str_1, str_2);

   if (res == 0) {
       printf("The strings are equal.\n");
   } 
   else if (res < 0) {
       printf("Str_1 is less than str_2.\n");
   } 
   else {
       printf("Str_1 is greater than str_2.\n");
   }
   return 0;
}

Output

After executing the above code, we get the following result−

Str_1 is less than str_2.

Example 4

Here, we use strcmp() to compare the two different string with the help of lexicographical order.

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

int main { 

   char str1[] = "text";
   char str2[] = "notebook";

   int result = strcmp(str1, str2);
   if (result < 0) {
       printf("'%s' comes before '%s' lexicographically.\n", str1, str2);
   } 
   else if (result > 0) {
       printf("'%s' comes after '%s' lexicographically.\n", str1, str2);
   } 
   else {
      printf("Strings are equal.\n");
   }
    return 0;
}

Explanation

In this code, str1 ("text") comes before str2 ("Notebook") lexicographically. The strcmp() function returns a negative value.

The above code produces the following result −

'text' comes after 'notebook' lexicographically.