Advertisement

---

Top

< Prev

Next >

The strncpy() is a string manipulation function defined in the cstring header file, which works on a string which is stored in a c-style char array and this function is used to copy the first n number of characters of a string to another string.

Signature of strcpy() function

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

• This function copies the first num, number of characters of source string to another destination string.
• The function returns a char[] array pointer, pointing to the destination string containing the just copied string value.

Example of strncpy() function

In the upcoming code, we are calling strncpy() function, to copy the first 2 characters of one string named arr2 to another string named arr1.

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

#include<iostream>
#include<cstring>

using namespace std;

int main()
{
char arr1[15] = "Keep Smiling";
char arr2[15] = "Always";

cout<< "The content of first string is : " << arr1 << "\n";
cout<< "The content of second string is : " << arr2 << "\n";

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

cout<< "The addition of two string is : " << arr1 << "\n";
cout<< "The content of second string : " << arr2;

return 0;
}

Output is -

The content of first string is : Keep Smiling
The content of second string is : Always
The addition of two string is : Keep SmilingAl
The content of second string : Always

• The first char[] array i.e. arr1 is initialized with a string value Keep Smiling and the second char[] array i.e. arr2 is initialized with the value Always.
• The function strncpy() copies the first 2 characters of string value in the arr2 char[] array to the end of first char[] array i.e. arr1.

Advertisement

Performing strncpy without using strncpy() function

Let's create a program copies the first n number of characters of one string to another string without using strncpy() function.

// Program to copy n, number of characters of one string to another string without strncpy() function 


#include<iostream>
#include<cstring>

using namespace std;

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

cout<< "The value in dest string : " << dest << "\n";
cout<< "The second in src string : " << src << "\n";

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

cout<< "Length of characters in dest string : " << len1 <<"\n";

int num; 
cout<< "How many characters of the first string you to copy from str string : ";
cin>>num;

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

cout<< "The new value in dest string : " << dest;

return 0;
}

Output is :

The value in dest string : Hello
The second in src string : World
Length of characters in dest string : 5
How many characters of the first string you to copy from str string: 2
The new value in dest string : Wollo

• 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 have manually copied to dest char[], replacing its content from Hello to Wollo.

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++ strncpy() function

< C++ strcmp() function >

Advertisement