Advertisement

---

Top

< Prev

Next >

The strncat() is a string function defined in the string.h header file, which is used to add the first n number of characters of a string to the end of another string.

Signature of strncat() function

char * strncat ( char * destination, const char * source, size_t num )

• This function appends the first num, number of characters of source string at the end of the characters present in the destination string.
• The function returns a char[] array pointer, pointing to the destination string containing the addition of both string values.

Example of strncat() function

In the upcoming code, we are calling strncat() function, to add first 2 characters of one string named arr2 at the end of characters present in another string named arr1.

/*  Program to append n number of characters of first string at the end of another string. */

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

int main()
{
char arr1[10] = "Have a ";
char arr2[10] = "good day!";

printf("The content of first string is : %s", arr1);
printf("\n");

printf("The content of second string is : %s", arr2);
printf("\n");

strncat(arr1,arr2,2); /* only first two characters from arr2 will be appended to the end of arr1 */

printf("The addition of two string is : %s", arr1);
printf("\n");
printf("The content of second string : %s", arr2);

return 0;
}

Output is -

The content of first string is : Have a
The content of second string is : good day!
The addition of two string in the first string : Have a go
The content of second string : good day!

• The first char[] array i.e. arr1 is initialized with a string value Have a and the second char[] array i.e. arr2 is initialized with the value good day!.
• The function strncat() appends first 2 characters of one string value in the arr1 char[] array at the end of characters present in the second char[] array i.e. arr2.

Advertisement

Adding two strings without using strncat()

Let's create a program appends the first n number of characters of one string at the end of another string without using strncat() function.

/* Program to append n, number of characters of one string at the end of another string without strcat() function */


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

int main()
{
char dest[20] = "Hello";
char src[10] = "World";

printf("The value in dest string : %s", dest);
printf("\n");

printf("The second in src string : %s", src);
printf("\n");

int len1 = strlen(dest);
int len2 = strlen(src);

printf("Length of characters in dest string : %d \n", len1);

int num; 
printf("How many characters of the first string you to append : ");
scanf("%d", &num);

for(int i=0;i<num; i++)
{
	dest[len1] = src[i];
	len1 = len1 + 1 ;
}
dest[len1]='\0';

printf("Concatenated strings : %s ", dest);

return 0;
}

Output is :

The value in dest string : Hello
The second in src string : World
Length of characters in dest string : 5
Length of characters in src string : 5
How many characters of the first string you to append : 3
Concatenated strings : HelloWor

• The first char[] array i.e. dest is initialized with a string value Hello and the second char[] array i.e. dest is initialized with the value World.
• Next, we have calculated the total length of characters actually present in the first char[] array, by using strlen() function.
• Next, we ask the user to enter the number of characters of the first string, which we manually append to the end of dest char[].

Note: - The function strlen returns the total number of characters actually present in the char[] and not the total number of character it can hold.

Please share this article -

< Prev

Next >

< C strcat() function

C strcpy() function >

Advertisement