int scanf(const char *format, ...);

The function returns the number of items that were successfully read
EOF if the input stream reached its end, or a negative number if an error occurs.

/* 
 * scanf example code
 * http://code-reference.com/c/stdio.h/scanf 
 */
 
#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 
 
int main ( void )
{
  char input[20];
 
  printf ("Enter some Text (max 20 chars) ");
  scanf ("%s",input);  
  printf ("Scanf input was %s.\n",input);
 
  return 0;
}

  output: ./scanf 
  Enter some Text (max 20 chars) Hello this is a test for scanf    
  Scanf input was Hello.

see also fscanf printf fprintf