strcat() vs strncat() in C++

strcat()

The strcat() function will append a copy of the source string to the end of destination string. The strcat() function takes two arguments: 
1) dest 
2) src 
It will append copy of the source string in the destination string. The terminating character at the end of dest is replaced by the first character of src .
Return value: The strcat() function returns dest, the pointer to the destination string. 

CPP

// CPP program to demonstrate
// strcat
#include <cstring>
#include <iostream>
using namespace std;
int main()
{
    char dest[50] = "This is an";
    char src[50] = " example";

    strcat(dest, src);
    cout << dest ;
    return 0;
}

Output:

This is an example

strncat()

The strncat() function in C++ appends the given number of character from one string to the end of another string.The strncat() function will take these three arguments: 
1) Dest 
2) Src 
3) Count
This will append the given number of characters from src string to the end of dest string. The terminating character at the end of dest string will be replaced by the first character of src string . 
Return value: The strncat() function returns dest, the pointer to the destination string. 

CPP

// CPP program to demonstrate
// strncat
#include <cstring>
#include <iostream>

using namespace std;

int main()
{
    char dest[25] = "This is an example";
    char src[50] = " to show working of strncat() this is not added";

strncat(dest, src, 29);
    cout << dest ;
    return 0;

}

Output: 

This is an example to show working of strncat()

How strncat() is different from strcat() ?

It is recommended by many of the programmers that strncat() is safe as compared to strcat() because strcat() does not check for the size of the copied data, and copies until it gets to a null terminator, it might cause a buffer overflow while strncat() check for the size of the copied data, and will copy only ‘n’ bytes.

CPP

// C,C++ program demonstrate difference between
// strncat() and strcat()
#include <stdio.h>
#include <string.h>

int main()
{

   // Take any two strings
   char src[50] = "forgeeks";
   char dest1[50] = "geeks";
   char dest2[50] = "geeks";

   printf("Before strcat() function execution, ");
   printf("destination string : %s\n", dest1);

   // Appends the entire string of src to dest1
   strcat(dest1, src);

   // Prints the string
   printf("After strcat() function execution, ");
   printf("destination string : %s\n", dest1);

   printf("Before strncat() function execution, ");
   printf("destination string : %s\n", dest2);

   // Appends 3 characters from src to dest2
   strncat(dest2, src, 3);

   // Prints the string
   printf("After strncat() function execution, ");
   printf("destination string : %s\n", dest2);

   return 0;
}

Output: 

Before strcat() function execution, destination string : geeks
After strcat() function execution, destination string : geeksforgeeks
Before strncat() function execution, destination string : geeks
After strncat() function execution, destination string : geeksfor

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