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memcpy() in C/C++

  • Difficulty Level : Basic
  • Last Updated : 06 Sep, 2021

memcpy() is used to copy a block of memory from a location to another. It is declared in string.h

// Copies "numBytes" bytes from address "from" to address "to"
void * memcpy(void *to, const void *from, size_t numBytes);

Below is a sample C program to show working of memcpy().

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C




/* A C program to demonstrate working of memcpy */
#include <stdio.h>
#include <string.h>
 
int main ()
{
  char str1[] = "Geeks"
  char str2[] = "Quiz"
 
  puts("str1 before memcpy ");
  puts(str1);
 
  /* Copies contents of str2 to str1 */
  memcpy (str1, str2, sizeof(str2));
 
  puts("\nstr1 after memcpy ");
  puts(str1);
 
  return 0;
}

Output: 

str1 before memcpy 
Geeks

str1 after memcpy 
Quiz

Notes: 
1) memcpy() doesn’t check for overflow or \0 
2) memcpy() leads to problems when source and destination addresses overlap. 

memmove() is another library function that handles overlapping well.
Write your own memcpy() and memmove()
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
 

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