what happens when you input things like 12ab to scanf(“%d”,&argu)?

Question

I came across this problem when I want to check what I input is number. The scanf function will return 1 if I successfully input a number. So here is what I wro

Answer 1

It's better to read a full line, using fgets(), and then inspecting it, rather than trying to parse "on the fly" from the input stream.

It's easier to ignore non-valid input, that way.

Use fgets() and then just strtol() to convert to a number, it will make it easy to see if there is trailing data after the number.

For instance:

char line[128];

while(fgets(line, sizeof line, stdin) != NULL)
{
   char *eptr = NULL;
   long v = strtol(line, &eptr, 10);
   if(eptr == NULL || !isspace(*eptr))
   {
     printf("Invalid input: %s", line);
     continue;
   }
   /* Put desired processing code here. */
}