//a function that copies one string to another
copy(char *,char*);
main()
{
char one[20],two[20];
printf("enter two sentences \n\n");
gets(one);//first string
gets(two);//second string
copy(one,two);
printf("%s",two);
}
copy(char *s1,char *s2)
{
while(*s1!='\0')
{
s2=s1;
s1++;
s2++;
}
s2='\0';
}
what wrong with the above program ? why the string 'one' is not getting copied to string 'two'?please explain with the help of pointer
It's because this:
s2 = s1;
changes the pointer s2 so that it points to the content of s1.
What you want to do is copy the content:
*s2 = *s1;
A decent compiler should also have given you a warning on this line:
s2 = '\0';
since you're assigning a char to a char *. It should be:
*s2 = '\0';
Enacting those changes, the function would then be (including using some, IMNSHO, better variable names):
void copy (char *from, char *to) {
while (*from != '\0') {
*to = *from;
from++;
to++;
}
*to = '\0';
}
Or, once your brain has been warped by several decades of C use like mine :-)
void copy (char *from, char *to) {
while (*to++ = *from++);
}
do...while loop? Isn't the while loop better?
do.while is that it checks the terminating condition after the iteration, meaning you don't need more code at the end to copy or put a string terminator.while loop better in this case(as there are less characters to type)? Also, I didn't mean the while loop in the answer... I meant using while (*to++ = *from++); instead of do {} while (*to++ = *from++);.#include <stdio.h>
#include <string.h> /* for strchr */
void copy(const char *, char*); /* use void to return nothing */
int main(void) /* main() is not valid */
{
char one[20], two[20];
char *ptr;
printf("enter two sentences \n\n");
/* gets is deprecated, use fgets in order to avoid overflows */
fgets(one, sizeof one, stdin);
/* fgets leaves a trailing newline, remove it */
if ((ptr = strchr(one, '\n'))) *ptr = '\0';
fgets(two, sizeof two, stdin); /* why? is gonna be replaced by one */
copy(one, two);
printf("%s\n", two);
return 0;
}
void copy(const char *s1, char *s2) /* s1 is not modified, use const */
{
while(*s1 != '\0')
{
*s2 = *s1; /* Don't assign addresses, assign values */
s1++;
s2++;
}
*s2 = '\0';
}
*-operator here:*s1!='\0'and do not use it here:s1=s2;and heres2='\0';.