Node:Other Input Conversions, Next:Formatted Input Functions, Previous:Dynamic String Input, Up:Formatted Input
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 (see 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.