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 12.14.7 Other Input Conversions
 -------------------------------
 
 This section describes the miscellaneous input conversions.
 
    The `%p' conversion is used to read a pointer value.  It recognizes
 the same syntax used by the `%p' output conversion for `printf' (
 Other Output Conversions); that is, a hexadecimal number just as the
 `%x' conversion accepts.  The corresponding argument should be of type
 `void **'; that is, the address of a place to store a pointer.
 
    The resulting pointer value is not guaranteed to be valid if it was
 not originally written during the same program execution that reads it
 in.
 
    The `%n' conversion produces the number of characters read so far by
 this call.  The corresponding argument should be of type `int *'.  This
 conversion works in the same way as the `%n' conversion for `printf';
 see  Other Output Conversions, for an example.
 
    The `%n' conversion is the only mechanism for determining the
 success of literal matches or conversions with suppressed assignments.
 If the `%n' follows the locus of a matching failure, then no value is
 stored for it since `scanf' returns before processing the `%n'.  If you
 store `-1' in that argument slot before calling `scanf', the presence
 of `-1' after `scanf' indicates an error occurred before the `%n' was
 reached.
 
    Finally, the `%%' conversion matches a literal `%' character in the
 input stream, without using an argument.  This conversion does not
 permit any flags, field width, or type modifier to be specified.
 

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