scanf unknown number of integers, how to end loop?

Question

In class I need to use scanf to get integers to work with. Problem is I do not know to end the while loop. I wait for \'\\n\' in the c

Answer 1

while(scanf("%d%c", &numbers, &ch)) { if((ch == '\n') .... has a couple of problems.

1. If the line of input has only white-space like "\n" or " \n", scanf() does not return until non-white-space is entered as all leading white-spaces are consumed by "%d".

2. If space occurs after the int, the "\n" is not detected as in "123 \n".

3. Non-white-space after the int is discarded as in "123-456\n" or "123x456\n".

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how to end loop?

Look for the '\n'. Do not let "%d" quietly consume it.

Usually using fgets() to read a line affords the more robust code, yet sticking with scanf() the goal is to examine leading white-space for the '\n'

#include <ctype.h>
#include <stdio.h>

// Get one `int`, as able from a partial line.
// Return status:
//   1: Success.
//   0: Unexpected non-numeric character encountered. It remains unread.
//   EOF: end of file or input error occurred.
//   '\n': End of line.
// Note: no guards against overflow.
int get_int(int *dest) {
  int ch;
  while (isspace((ch = fgetc(stdin)))) {
    if (ch == '\n') return '\n';
  }
  if (ch == EOF) return EOF;
  ungetc(ch, stdin);
  int scan_count = scanf("%d", dest);
  return scan_count;
}

Test code

int main(void) {
  unsigned int_count = 0;
  int scan_count;
  int value;
  while ((scan_count = get_int(&value)) == 1) {
    printf("%u: %d\n", ++int_count, value);
  }
  switch (scan_count) {
    case '\n': printf("Normal end of line.\n"); break;
    case EOF: printf("Normal EOF.\n"); break;
    case 0: printf("Offending character code %d encountered.\n", fgetc(stdin)); break;
  }
}