Bdtjtk

So, I have this string
char currentString[212] = { 0 };

and after I'm using it once, I want to reset it.
I triend many ways, such as:

for (int k = 0; k < strlen(currentString); k++)

{

    currentString[k] = '';

}

but it won't go over the loop more than once, and it give '' only to the first char, the rest remain the same.

and I also tried:

currentString[0] = '';

yet I get the same result.

any suggestions for what can I do?
thanks!

strlen will find the length by searching for the first occurrence of . So if you want to reset the whole array, you should change strlen(currentString) to sizeof currentString. However, do note that this will not work with pointers.

If you pass the array to a function, you cannot determine the size of the array afterwards, so this will not work:

void foo(char * arr) {

    for (int k = 0; k < sizeof arr; k++) 

        arr[k] = '';

}

Instead you need to do like this:

void foo(char * arr, size_t size) {

    for (int k = 0; k < size; k++) 

        arr[k] = '';

}

But of course there's no reason to write custom functions for this when memset is available.

Imagine char currentString = "abc"; and then running you loop:

• k = 0


• initialy strlen(currentString) = 3, there are 3 characters before '' byte. the loop condition k < strlen(currentString) is true


• 
  k = 0 -> currentString[0] = ''
  


• 
  k++ -> k = 1
  


• then strlen(currentString) = 0 (as the first byte of currentString is equal to '', there are no characters before '')


• the loop condition is false k < strlen(currentString) -> 1 < 0
  

So the loop will always run only one time.

If you want to write only zero bytes to a memory region, use memset

 memset(currentString, 0, sizeof(currentString));

will set the memory region as pointed to by currentString pointer with sizeof(currentString) bytes to zeros.

Setting the first byte to zero:

 currentString[0] = '';

maybe considered enough to "clear a string".

to zero the whole array

char arr[SOMESIZE];



/* ... */



memset(arr, 0, sizeof(arr));

pointer - you need to know the size of the allocated memory as sizeof will return the size of the pointer itself only, not the referenced object;

char *p = malloc(SIZE);

/* ..... */

memset(p, 0 , SIZE);

Setting the first byte to '' wont clear out the currentString.You may think that because ANSI C thinks that is a string terminator and if you print your string it will show empty.But if you check the second byte you will see the second char from your string. As other's said the best option to wipe out the string is:

memset(currentString, 0, sizeof(currentString));

And is way safer and faster.Also in ANSI C 0 and '' are the same.

It is never a good decision to calculate anything again and again. Instead you should calculate the strlen() only once.
That being said, in your case, doing so will solve the problem, as the reason it didn't work was that strlen() returned 0 right after the first round, since the length of the string became 0.

int n = strlen(currentString);

for (int k = 0; k < n; k++)

{

    currentString[k] = '';

}