forcing the buffer to clear in scanf

Question

i have a problem with scanf and input buffer in my program.

first i ask the user for input :

char someVariable;
printf("Enter text: ");
scanf(" %c",&someVariable);

and then i have a loop that goes over the input one char at a time in scanf until it reaches \n. the problem is that after the loop is done, somehow, there is still something in the buffer so this function (which is being called in a loop) gets called again and ruins the logic in my program.

how can i force clear the input buffer?

i can only use scanf (assignment requirements)

void checkType(){
    char userInput;
    char tempCheckInput;
    printf("Enter Text: ");
    scanf(" %c",&userInput);
    while (userInput != '\n'){

        tempCheckInput = userInput;
        scanf("%c",&userInput);

ignore the end of the loop, that's the part i get the input

@user3386109 it's a long..ish program so i don't want to copy over 100 lines, i'll edit the post one sec — DarkLeader, Nov 16 '19 at 22:19

score 3 · Accepted Answer · answered Nov 16 '19 at 22:46

how can i force clear the input buffer?

In C, a stream, like stdin, cannot be cleared (in a standard way) as in "delete all input up to this point in time".

Instead input can consume and toss (akin to "cleared") input up to a data condition.

The usually way is

int consume_rest_of_line(void) {
  int ch;
  while ((ch = getchar()) != '\n' && ch != EOF) {
    ;
  }
}

If limited to scanf()

int consume_rest_of_line(void) {
  char ch;
  while (scanf("%c", &ch) == 1 && ch != '\n') {
    ;
  }
}

forcing the buffer to clear in scanf

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