Thread: Questions on String functions!

what is wrong with this function which acts like strncpy

Code:

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

void xstrncpy(char *s, int n);

int main()
{
  int n;
  char s[80];
  printf("\nEnter the string\n");
  scanf("%s",s);
  printf("\nEnter the number of characters to be copied");
  scanf("%d",n);
  xstrcpy(s,n);
  getch();
  return 0;
}

void xstrncpy(char *s, int n)
{
     int i;
     char s1[80], *s2;
     s2=s1;
     for(i=1;i<=n;i++)
     {
	 *s2=*s;
	 s2++;
	 s++;
     }
 *s2='\0';
 printf("S1 = %s",s1);

}

and this which is for strset

Code:

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

void xstrset(char *s, char c);

int main()
{
	char s[]="apocalypse";
	char c='a';

	xstrset(s,c);

	return 0;
}

void xstrset(char *s, char c)
{
	while(*s)
	{
		*s=c;
		s++;

	}
	printf("%s",s);
}

and this which reverses and string

Code:

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

void xstrrev(char *s, char *s1);

int main()
{
	char s[]="sasdh";
	char s1[10];

	xstrrev(s,s1);

	return 0;
}

void xstrrev(char *s, char *s1)
{
	int len,i;
	len=strlen(s);
	while(*s!='\0')
	{
		s++;
	}

	while(len!=0)
	{
		s--;
		*s1=*s;
		len--;
	}
	*s1='\0';
	printf("%s",s1);
}

Also i want to write a custom function for strstr. Can anyone pls help me for this?

Wrong with xstrncpy is that you are moving the pointer. At the end, the pointer is pointing to the string and therefor you see nothing when printing. It can be done a little easier, assumed is that dest has enough memory.

Code:

void xstrncpy (char *dest, char *src, int n)
{
     int i = 0;
     
     while (src [i] != NULL && i < n)
     {
        dest [i] = src [i];
        i++;
     }
}

I tried in this , but it doesnt work. Why so?

Code:

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

void xstrncpy(char *s, int n);

int main()
{
  int n;
  char s[80];
  printf("\nEnter the string\n");
  scanf("%s",s);
  printf("\nEnter the number of characters to be copied");
  scanf("%d",n);
  xstrncpy(s,n);
  getch();
  return 0;
}

void xstrncpy(char *s, int n)
{
     int i=1;
     char s1[80], *s2;
     while(s[i]!='\0' && i<=n)
     {
	 s1[i]=s[i];
	 i++;
     }
     *s2='\0';
     printf("S1 = %s",s1);

}

Please help.

Got it . Thanx