strncmp in C language

The C strncmp function is one of the String Function, which is used to compare two strings. Or it is used to check whether those two strings are equal or not. strncmp function uses third argument to limit the comparison. It means, instead of comparing whole string, you can compare first four characters, or five characters etc.

In this article we will show you, How to use strncmp in C Programming language with example. The strncmp method returns any of the following three values:

• This will return -1, if str1 is less than str2
• This will return +1, if str1 is greater than str2
• Function will return 0, if str1 and str2 are equal

C strncmp syntax

The basic syntax of the strncmp in C Programming language is as shown below.

char *strncmp(char *str1, char *str2, size_t n);

or we can simply write this strncmp is as shown below:

strncmp(str1, str2, string_length);

• n: The maximum number of character that you want to compare.

strncmp in C language Example

The strncmp function is used to compare user specified string with existing string for n number of characters. This program will help you to understand the strncmp with multiple examples.

TIP: You have to include the #include<string.h> header before using this strncmp string function.

/* C strncmp Function example  */

#include <stdio.h> 
#include<string.h>
 
int main()
{
   char str1[50] = "abcdef";
   char str2[50] = "abcd";
   char str3[] =  "ghi";
   int i, j, k;
	
   i = strncmp(str1, str2, 4);		
   printf("\n The Comparison of str1 and str2 Strings = %d", i);
 	
   j = strncmp(str1, str2, 6);		
   printf("\n The Comparison of str1 and str2 Strings = %d", j);
   
   k = strncmp(str1, str3, 3);		
   printf("\n The Comparison of str1 and str3 = %d", k);
}

OUTPUT

ANALYSIS

This will compare first four characters because, third argument is 4.

i = strncmp(str1, str2, 4); // abcd = abcd

This statement will compare first six characters because, third argument is 6.

j = strncmp(str1, str2, 6); // abcdef = abcd

strncmp in C Example 2

Instead of printing 0, 1, and -1 as the result, this strncmp program will print a meaningful message using Else If Statement

/* C strncmp Function example  */

#include <stdio.h> 
#include<string.h>
 
int main()
{
   	char str1[50] = "abcdefgh";
   	char str2[50] = "ABC";
   	int result;
	
   	result = strncmp(str1, str2, 3);
   
   	if(result < 0)
   	{
   		printf("\n str1 is Less than str2");
	}
	else if(result > 0)
   	{
   		printf("\n str2 is Less than str1");
	}
	else
   	{
   		printf("\n str1 is Equal to str2");
	}
	return 0;
}

OUTPUT

strncmp Example 3

This program allows the user to enter two strings. Next, it is going to compare those two strings using strncmp function in C programming.

/* string strncmp in C programming Example */
 
#include <stdio.h> 
#include<string.h>
 
int main()
{
	char str1[100], str2[100];
	int result;
 
	printf("\n Please Enter First String  : ");
	gets(str1);	
	
	printf("\n Please Enter the String that you want to Compare : ");
	gets(str2);	
	
	result = strncmp(str1, str2, 4);
	
 	if(result < 0)
   	{
   		printf("\n First String is Less than Second String");
	}
	else if(result > 0)
   	{
   		printf("\n Second String is Less than First String");
	}
	else
   	{
   		printf("\n First String is Equal to Second String");
	}
	
}

OUTPUT

Let me change the Size value, and see the result