strncmp() In C

Purpose of strncmp()

strncmp() is one of the inbuilt string function in c programming which is used to compare two strings up to specified length, if the strings are same up to specified length, it returns 0. Otherwise it returns a nonzero value.

How strncmp() Works

The following diagram clearly illustrate the working principle of strncmp() inbuilt string function in C.

In the above diagram, strncmp() compares first n characters of two strings.

Syntax - strncmp()

• strcmp() accepts three parameters.
• First two parameters are strings whereas third parameter is a integer.
• To use strncmp() inbuilt string function in C, we need to declare #include<string.h> header file.

strncmp(str1, str2, n);

C Program - strncmp()

Let us work through strncmp() function, In the following program we will compare two strings up to specified length n.

#include <stdio.h>
#include<string.h>
int main()
{
char str1[20] = "this is strncmp", str2[20] = "this is awesome";
if(strncmp(str1, str2, 8) == 0)
printf("The strings str1 and str2 are same up to 8 characters ");
return 0;
}

The strings str1 and str2 are same up to 8 characters

C Program - Without strncmp()

Let us compare two strings up to specified length without using any inbuilt string functions.

#include <stdio.h>
#include<string.h>
int main()
{
char str1[20] = "thi is strcmp";
char str2[20] = "this is strcmp";
int n=4, i, j=0;
for(i=0; i<n; i++){
if(str1[i] == str2[i])
j++;
}
if(n == j)
printf("The strings str1 and str2 are equal");
else
printf("The string str1 and str2 are unequal");
return 0;
}

The string str1 and str2 are unequal

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