strncat() in C

Purpose of strncat()

strncat() is one of the inbuilt string function in c programming which is used to combine two strings to form a single one up to a specified length n.

How strncat() Works

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

In the above diagram strncat() takes three parameters say str1, str2 and n. Here str1 and str2 are strings whereas n is of integer datatype. strncat() simply append n number of characters from str2 to str1.

Syntax - strncat()

• strncat() accepts three parameters.
• str1 is a string which is of character datatype.
• str2 is also a string which is of character datatype.
• n is a number which is of integer datatype.
• Here n describes, how much characters should we need to append from str2 to str1.
• To use strncat() inbuilt string functions in C, we need to declare #include<string.h> header file.

strncat(str1, str2, n);

C Program - Using strncat()

Let us work through strncat() function, In the following program we will append n characters from string 2 to string 1 by using strncat() inbuilt string function.

#include <stdio.h>
#include<string.h>
int main()
{
char str1[30] = "You are ";
char str2[30] = "cute in the world";
strncat(str1, str2, 4);
printf("%s", str1);
return 0;
}

You are cute

C Program - Without strncat()

Let us append n characters from string 2 to string 1 without using inbuilt string function strncat().

#include <stdio.h>
#include<string.h>
int main()
{
char str1[30] = "You are ";
char str2[30] = "cute in the world";
int i, j, n = 4;
for(i=0; str1[i]!='\0';i++){
//making using of variable i
}
for (j=0;j<n;j++){
str1[i] = str2[j];
i++;
}
printf("%s", str1);
return 0;
}

You are cute

Did You Know?

When str2 containing '\0' in its middle i.e) c\0ute in the world, then strncat() will terminate instead of skipping the null character.

#include <stdio.h>
#include<string.h>
int main()
{
char str1[30] = "You are ";
char str2[30] = "c\0ute in the world";
strncat(str1, str2, 4);
printf("%s", str1);
return 0;
}

You are c

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