How To Check Null In C 7 Steps With Pictures

if(ptr == NULL){ // code if pointer is NULL} else { // code if not NULL}

if (ptr != NULL) { // code if not NULL}

This looks a little awkward to some programmers, but it’s perfectly valid. Which approach you use just depends on personal preference, and how good your compiler is at detecting the if (ptr = NULL) error.

The reverse of this is if (!ptr), which will return TRUE if ptr is FALSE.

Avoid this mistake:char *ptr;if(ptr == NULL){//This will return FALSE. The pointer has been assigned a valid value. } Instead write:char *ptr = NULL; //This assigns the pointer to NULLif(ptr == NULL){//This will return TRUE if the pointer has not been reassigned. }

int *ptr = malloc(N * sizeof(int));if (ptr) { int i; for (i = 0; i < N; ++i) ptr[i] = i;}