Understanding why the newline is caught on the next iteration - c

Question

I wrote the following code:
int VALUE = 10;
int counter = 0;
char c;
while (true) {
if(scanf("%c", &c) != 1) {
return NULL;
}
if (c == '\n') {
break;
}
if (counter % VALUE < VALUE - 1) {
num[counter] = c;
counter++;
} else {
char* temp = (char*) malloc((counter + MAX_VALUE)*sizeof(char));
if (temp == NULL) {
return NULL;
}
for (int i = 0; i < counter; i++) {
temp[i] = num[i];
}
free(num);
num = temp;
num[counter] = c;
counter++;
}
}
printf("counter = %d\n",counter);
It doesn't really matter what it does but I have some problem with the counter. For some reason, when I insert 9876.54321 (newline at the end), It does not enters into the if (c == '\n') { break; } block when it scanfs \n, only on the next iteration. The length of 9876.54321 is 10 but it will print 11. What is the reason? I also tried to switch to getchar() but I get the same thing.

Answer 1

Here:
if(scanf("%c", &c) != 1) {
%c in scanf leaves the leading and following whitespace in the input buffer.
To fix this, don't use scanf. Use getchar or getc instead. Instead of using c == '\n', use isspace(c).
Don't do char c. You can't check for EOF if you do that. Instead, use int c.
Full code sample:
int VALUE = 10;
int counter = 0;
int c;
while (true) {
c = getchar();
if (isspace(c) || c == EOF) {
break;
}
if (counter % VALUE < VALUE - 1) {
num[counter] = c;
counter++;
} else {
char* temp = (char*) malloc((counter + MAX_VALUE)*sizeof(char));
if (temp == NULL) {
return NULL;
}
for (int i = 0; i < counter; i++) {
temp[i] = num[i];
}
free(num);
num = temp;
num[counter] = c;
counter++;
}
}
printf("counter = %d\n",counter);