Read formatted data from stdin.
  Reads data from the standard input (stdin) and stores it into the locations given by argument(s). Locations pointed by each argument are filled with their corresponding type of value requested in the format string.
  There must be the same number of type specifiers in format string than arguments passed.

Parameters.

format

String that can contain one or more of these items:

• Whitespace characters: the function will read and ignore any whitespace characters (this includes blank, newline and tab characters) encountered before the next non-whitespace character. This includes any quantity of whitespace characters (including none).
  
• Non-whitespace characters (any character not including blank, newline, tab, or any format specifier begining with % character): this cause that the function read and discard any character that match the given non-whitespace character. If this character is not found the function ends returning error.
• Format specifiers: A sequence of characters begining with '%' indicates that next data has to be readed and stored at the location pointed by its corresponding argument with a given format that is specified following this prototype:

  %[*][width][modifiers]type
   
    where:

  *	Data is read but ignored. It is not assigned to the corresponding argument.
  width	Specifies the maximum number of characters to be read.
  modifiers	Specifies a different size for the data pointed by argument: h   : short int l   : long int (if integer) or double (if floating point). L   : long double
  type	Character specifying the type of data that is expected and how it has to be read. See next table.

  *scanf types:
  

  type	Qualifying Input	Argument required
  c	Single character: Reads the next character (whitespace characters included).	char *
  d	Decimal integer: Number optionally preceeded with a sign.	int *
  e,E,f,g,G	Floating point: Decimal number containing a decimal point, optionally preceeded by a sign and optionally folowed by the e or E character and a decimal number. Valid entries are -732.103 or 7.12e4	float *
  o	Octal integer.	int *
  s	String of characters. This will read subsequent characters until a whitespace is found (whitespace characters are blank, newline and tab).	char * (string)
  u	Unsigned decimal integer.	unsigned int *
  x	Hexadecimal integer.	int *

  
  

argument(s)

pointer to objects or structures to be filled with data read as specified by format string. There must be the same number of these parameters than the number of format tags.
NOTE: These arguments must be pointers: if you want to store the result of a scanf operation on a standard variable you should precede it with the reference operator, i.e. an ampersand sign (&), like in:

int n;
scanf ("%d",&n);

Return Value.
  The number of items succesfully read. This count doesn't include any ignored fields with asterisks (*).
  If EOF is returned an error has occurred before the first assignation could be done.

Portability.
  Defined in ANSI-C.

Example.

/* scanf example */
#include <stdio.h>

main ()
{
  char str [80];
  int i;

  printf ("Enter your surname: ");
  scanf ("%s",str);  
  printf ("Enter your age: ");
  scanf ("%d",&i);
  printf ("Mr. %s , %d years old.\n",str,i);
  printf ("Enter a hexadecimal number: ");
  scanf ("%x",&i);
  printf ("You have entered %#x (%d).\n",i,i);
  
  return 0;
}

See also.
  fscanf, printf, fopen, fclose