Thread: Clearing elements in an array.

If you're just going to overwrite the current data, there's no point in clearing it. If you want to do this for debugging purposes, just fill the array with a zero value. By 'zero value' I mean something predictable but appropriate for the type and use of the array. It doesn't actually have to be 0.

Just terminate your string with a null character correctly, and you don't have to worry about overwriting it. However, if you still want to, consider looking at the memset function.


Quzah.

Originally Posted by ReXXuSS

Code:

for (i = 0; i != '\0' ; i++){
     string[i] = ' ';
}

well --- your example will do nothing at all. Why? the loop starts out by setting i to be 0, then it wants to continue the loop as long as i is not 0, but since i is initialized to 0 the loop will do nothing. maybe something like this is intended. Note that it is faster and more efficient than using the loop approach. This approach will only work when string is a char*. To set arrays of other data types, such as int, to something other than 0 you need the loop.

Code:

memset(string,' ',strlen(string));

Both are incorrect however, because by "clearing" a string, you wouldn't set it to all spaces. If you did, and you were doing as the OP states by just copying the new string (minus the null) over top, it would still run the full length of the allocated space, because you've got it full of spaces. That is to say, if the string was 10 characters, and you space filled it, then copied "bob" to it, every time you wanted to print the string, or what not, you'd get:

Code:

"bob       "

I somehow don't think that's what they had in mind.


Quzah.

I think it should be:

Code:

memset(string,'\0',strlen(string)-1);

Originally Posted by Ene Uran

I think it should be:

Code:

memset(string,'\0',strlen(string)-1);

That's an interesting thought, but the original was correct. Try it out by "clearing" the string with spaces.

@OP: Why is simply setting the first character of the string to be cleared to 0 insufficient?

Code:

int main()
{
	char a[] = "awesome";
	printf("%s\n",a);
	a[0] = 0;
	printf("%s\n",a);
	return 0;
}

[edit]Nevermind, it made more sense after reading it the second time.

Originally Posted by pianorain

Why is simply setting the first character of the string to be cleared to 0 insufficient?

Or as stated in my first reply, why not just copy the null character over when you copy in your new string?


Quzah.