strncpy adavnced :P

Hello everybody,

I just started to learn C, so I hope you don't mind that I will post here the newbie-problems I do run into. I am learning C as a hobby, just as I learned Basic, Pascal and VB(A) in the past. So now I want to learn the "famous C" :P.

Well, here we go....

You can use "strncpy' to copy a number of characters from one string to another. That is handy, but what I really would like is that I can copy a number of characters from a given position in the source string to the destination string. I tried some things....

Having in mind that a string in C is an array of char, I tried this:

strncpy(dest_str, source_str[3], 10)

I hoped that strncpy would start at position 4 of the source string and copied 10 characters. But when I compiled the program, the compiler told me that it hated me and stopped :P.

Then I thought that maybe a pointer could help me. So I tried the next something

Code:

---

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

int main()
{
        char regel1[30];
        char regel2[30];

        char *ptr;

        strcpy(regel1, "Programing is fun and relaxing to do");
       

        ptr = &regel1[10];
        strncpy(regel2, *ptr, 3);
       
}

---

But after that I got an casting error.

Okay, so how to solve this problem... can I use "strncpy" at all to get done what I want? I mean, something like that would be nice for other functions as "memset" too.

Thank you already for your answering and advices.

Joke.
(BTW the name Joke is no joke :). It is very common Dutch girls name and is pronounced as "jo-ke" and not as the English word joke).

strncpy( regel2, &regel1[10], 3 );
You were pretty close.

BTW, strncpy doesn't append a \0 (like strcpy does), so you have to do that yourself.
regel2[3] = '\0';

Not sure of your intent on using

Code:

---


ptr = &regel1[10];

---

Remove that and simply call

Code:

---

strncpy(regel2, regel1, 3);

---

Should do the trick

Sorry, noticed my flaw. Just change your ptr* to simply be ptr. Overlooked that you wanted to start at position 10 of your string array.

Code:

---


strncpy(regel2, ptr, 3);

---

Also

If the array pointed to by s2 is a string that is shorter than n bytes, null bytes are appended to the copy in the array pointed to by s1, until n bytes in all are written.