In this article, you will learn about C string library function memcpy( ) that is related to memory with step by step explanation and example.

Since memcpy( ) is the standard library function defined in string.h header file, we should include string library before using it.

#include<string.h>

Function prototype of C string library function memcpy( )

void *memcpy( void *str1, const void *str2, size_t n );

where,

               str1 = Pointer to the destination array or object where content will be copied

               str2 = Pointer to the source array or object from where content will be copied

               n = size of content to be copied in bytes

This C string library function memcpy( ) copies n characters from the block of memory pointed by str1 to str2.

It returns a pointer to the block of memory or object where contents are copied.

Note: The pointers are declared as void * so that they can be used for any data type.

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This function does not check for terminating null character ‘\0’.

If you want to copy the characters in a same part of memory then we should use another string library function memmove( ) because the result of memcpy( ) is undefined in such cases.

C program to demonstrate the use of string library function memcpy( )

/*Use of string library function memcpy*/

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

int main()
{
   //declaring and initializing character array
   char str1[ 50 ];
   char str2[ ] = "Learn C from trytoprogram.com";

   //displaying str1 and str2
   printf("str1 = %s\n", str1);
   printf("str2 = %s\n", str2);

   memcpy(str1, str2, strlen(str2) + 1);

   printf("\nAfter copying str2 into str1 using memcpy\n"
          "\nstr1 = %s\n", str1);

   return 0;
} //end

Output

Explanation

In the above program, we have used two standard string function memcpy( ) and strlen( ).

strlen( ) is used to determine the length of str2.