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scanf
=====

Syntax
------

     #include <stdio.h>
     
     int scanf(const char *format, ...);

Description
-----------

This function scans formatted text from `stdin' and stores it in the
variables pointed to by the arguments.  scanf:.   

The format string contains regular characters which much match the input
exactly as well as a conversion specifiers, which begin with a percent
symbol.  Any whitespace in the format string matches zero or more of any
whitespace characters in the input.  Thus, a single space may match a
newline and two tabs in the input.  All conversions except `c' and `['
also skip leading whitespace automatically.  Each conversion specifier
contains the following fields:

   *  An asterisk (`*') which indicates that the input should be
     converted according to the conversion spec, but not stored
     anywhere.

   *  A width specifier, which specifies the maximum number of input
     characters to use in the conversion.

   *  An optional conversion qualifier, which may be `h' to specify
     `short', `l' to specify long ints, or `L' to specify long doubles.
     Long long type can be specified by `L' or `ll'.

   *  The conversion type specifier:

    `c'
          Copy the next character (or WIDTH characters) to the given
          buffer.

    `d'
          Convert the input to a signed integer.

    `e'
    `E'
    `f'
    `g'
    `G'
          Convert the input to a floating point number.

    `i'
          Convert the input, determining base automatically by the
          presence of `0x' or `0' prefixes.  strtol:.   

    `n'
          Store the number of characters scanned so far into the
          integer pointed to.

    `o'
          Convert the input to a signed integer, using base 8.

    `p'
          Convert the input to a pointer.  This is like using the `x'
          format.

    `s'
          Copy the input to the given string, skipping leading
          whitespace and copying non-whitespace characters up to the
          next whitespace.  The string stored is then `NULL'-terminated.

    `u'
          Convert the input to an unsigned integer.

    `x'
    `X'
          Convert the input to an unsigned integer, using base 16.

    `[...]'
          Like the `c' format, except only certain characters are
          copied.  The characters between the brackets determine which
          characters are allowed, and thus when the copying stops.
          These characters may be regular characters (example:
          `[abcd]') or a range of characters (example: `[a-d]').  If
          the first character is a caret (`'), then the set specifies
          the set of characters that do not get copied (i.e.  the set
          is negated).  To specify that the set contains a
          close-bracket (`]'), list that as the first regular character.

    `%'
          This must match a percent character in the input.

Most conversions make use of `strtol' or `strtoul' to perform the
actual conversions.

Return Value
------------

The number of items successfully matched and assigned. If input ends
before first item is assigned, EOF is returned.

Example
-------

     int x, y;
     char buf[100];
     scanf("%d %d %s", &x, &y, buf);
     
     /* read to end-of-line */
     scanf("%d %[\n]\n", &x, buf);
     /* read letters only */
     scanf("[a-zA-Z]", buf);