Thread: Fgets not reading stdin. Help please.

I'm creating a simple function that reads three letters. The problem is, gdb shows me that the printf inquiry occurs after all the fgets and suggested newline elimination loops. Here's what gdb says in a nutshell.

74 printf("Please enter a subject: ");
(gdb) s
75 fgets(input, 5, stdin);
(gdb) s
.
.
.
84 printf("%s\n", input);
(gdb) s
Please enter a subject:
.
.
.
So I end up with an infinite number of inquiries. I don't even get the opportunity to enter in any letters. Please Help!

Code:

void find_subject( int **crns, char ***subjects, char ***courses,
     int *count )
{
  char input[20];
  int i;

  printf("Please enter a subject: ");
  fgets(input, 5, stdin);
  for ( i = 0 ; i < 20 ; i++ )
  {
    if ( input[i] == '\n' )
    {
        input[i] = '\0';
        break;
    }
  }
  printf("%s\n", input);
}

stdout is usually line-buffered by default, which means you won't see the output until you print a newline character. You can force the buffered output to print by flushing stdout with fflush(stdout); before calling an input function.

Uhh, I'm totally flabbergasted by your answer. What is stdout? I don't have any stdout in my code. What do you mean by flushing? I have never heard of the function fflush. Should I just type that before my printf? More help would be appreciated.

So now I've got a new problem. I've adjusted my code according to a FAQ. It is now

Code:

void find_subject( int **crns, char ***subjects, char ***courses,
     int *count )
{
  char input[4], str[4];
  int i, j;

  while (( i = getchar()) != '\n' && i != EOF);
    printf("Please enter a subject: ");
  if (fgets(input, 4, stdin))
  {
    for ( j = 0 ; j <= *count ; j++ )
    {
      strcpy(str, (*subjects)[j] );
      if ( str == input )
        printf("%i %s %s\n", (*crns)[j], (*subjects)[j], (*courses)[j]);
    }
  }
  printf("\n");
}

The problem is, I have an infinite loop. gdb shows that thing cycles endlessly between the for loop and strcpy. It never reaches the if statement. Why?

Also, flush isnt working for me. I get the same old problem if I enter the code. Endless prompts and never a chance to enter the subject.

Code:

printf("Please enter a subject: ");
    fflush (stdout);
    fgets( input, 4, stdin );

I'm using Unix if the information matters.

Originally Posted by Click_here

It's not there by default - It is included in stdio.h

Well, I meant in printf().... I should have explicitly indicated actually...

That did it! Thank you click here!