Thread: Example of struct in book causing a headache

This could help Flush the input buffer

Code:

     84     if (scanf("%d", &nfl.points) != 1)
     85             printf("Please try again\n");
     86
     87     while ((ch = getchar()) != '\n' && ch != EOF);
     88      {
     89     if (scanf("%d", &nfl.yards) != 1)
     90             printf("Please try again\n");
     91      }

-reading what getchar does I am puzzled how this while loop solved my problems. I declared int ch; in program also. This loop seems to clear out string from previous if statement. Can someone explain why this works now? I am using link you posted above but still confused.

Well I am guessing it just verifies there is data in stdin and overwrites those contents??

-Also how could I add code to make user enter a correct number instead of using printf and exiting with no valid input?

And more importantly utilize the quotee below:

fgets( buff, BUFSIZ, stdin );
Then validate buff in whatever way you choose, and copy the data to it's final destination.

Do I just assign buff = nfl.points and then see ifisdigit?

if user pesses something like
qw<ENTER>
scanf("&#37;d"...
will not be able to read anything from the stream leaving 3 chars there
'q' , 'w' , '\n'

while loop added just reads all chars till it encounters \n - leaving stdin empty

so probably your alltogether loop should be

Code:

while(scanf("%d",&nfl.points) != 1)
{
   /* clean the stdin */
   int ch;
   while ((ch = getchar()) != '\n' && ch != EOF);

   /* and try again */

   printf("Please try again\n");
}

/* succesfully read nfl.points number - could continue*/

Do I just assign buff = nfl.points and then see ifisdigit?

no, if you want to use fgets approch - it will be like

Code:

char buffer[BUFSIZ];
char* res;
while((res = fgets(buffer,sizeof buffer, stdin)) != NULL)
{
   if(sscanf(buffer, "%d" , &nfl.points) != 1) /* we can use strtol to make more carefull testing of the user input */
   {
      /* successfully read number */
      break;
   }
   /* line format was incorrect */
   printf("Please try again\n");
}

if(res == NULL)
{
   /* fgets failed - probably EOF riched - need to abort */
   return -1;
}

/* successfully read number - we can continue */

Originally Posted by cjohnman

I will add to my program both methods you explained. Thanks for the help!

do not mix fgets and scanf in the same program - stick to one method - or read everything with fgets and then convert

or use scanf - without need for convert...

mixing them could bring unexpected bugs in your code due to scanf leaving \n in stdin and next fgets reading it instead of the next string...