how to implement implementation of strncpy in c

Implementing strncpy in C: A Step-by-Step Guide

To implement the strncpy() function in C, you can use the following steps:

Include the necessary header files.

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

Define the prototype for the strncpy() function.

char *strncpy(char *dest, const char *src, size_t n);

This function takes three arguments:

• dest: A pointer to the destination array where the content is to be copied.
• src: The string to be copied.
• n: The number of characters to be copied from source.

Implement the strncpy() function.

The following code shows a simple implementation of the strncpy() function:

char *strncpy(char *dest, const char *src, size_t n) {
  if (n != 0) {
    register char *d = dest;
    register const char *s = src;
    do {
      if ((*d++ = *s++) == 0) {
        /* NUL pad the remaining n-1 bytes */
        while (--n != 0) *d++ = 0;
        break;
      }
    } while (--n != 0);
  }
  return (dest);
}

This function copies up to n characters from the source string (src) to the destination string (dest). If the length of the source string is less than n, the remainder of the destination string is padded with null bytes.

Test the strncpy() function.

You can test the strncpy() function using the following code:

int main() {
  char dest[100];
  char src[] = "This is a test string.";

  strncpy(dest, src, 20);

  printf("The copied string is: %s\n", dest);

  return 0;
}

This code copies the first 20 characters from the source string to the destination string. The output of the program is:

The copied string is: This is a test str

You can change the value of n to copy different numbers of characters from the source string.

Further Reading:

Implementation of strncat() in C

add source string at the end of destination string

comparing two string using strcmp and strncmp

Design a function to copy to copy string into destination string using strcpy and strncpy

how to implement implementation of strncpy in c

Design a function to calculate the length of the string using strlen

pre defined string based function

Design a function using my_strcpy and using my_strchr we need to select given char in given string

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