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(libc.info)Variable Arguments Input

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Variable Arguments Input Functions
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   The functions `vscanf' and friends are provided so that you can
define your own variadic `scanf'-like functions that make use of the
same internals as the built-in formatted output functions.  These
functions are analogous to the `vprintf' series of output functions.
Note: Variable Arguments Output, for important information on how to
use them.

   *Portability Note:* The functions listed in this section were
introduced in ISO C99 and were before available as GNU extensions.

 - Function: int vscanf (const char *TEMPLATE, va_list AP)
     This function is similar to `scanf', but instead of taking a
     variable number of arguments directly, it takes an argument list
     pointer AP of type `va_list' (Note: Variadic Functions).

 - Function: int vwscanf (const wchar_t *TEMPLATE, va_list AP)
     This function is similar to `wscanf', but instead of taking a
     variable number of arguments directly, it takes an argument list
     pointer AP of type `va_list' (Note: Variadic Functions).

 - Function: int vfscanf (FILE *STREAM, const char *TEMPLATE, va_list
          AP)
     This is the equivalent of `fscanf' with the variable argument list
     specified directly as for `vscanf'.

 - Function: int vfwscanf (FILE *STREAM, const wchar_t *TEMPLATE,
          va_list AP)
     This is the equivalent of `fwscanf' with the variable argument list
     specified directly as for `vwscanf'.

 - Function: int vsscanf (const char *S, const char *TEMPLATE, va_list
          AP)
     This is the equivalent of `sscanf' with the variable argument list
     specified directly as for `vscanf'.

 - Function: int vswscanf (const wchar_t *S, const wchar_t *TEMPLATE,
          va_list AP)
     This is the equivalent of `swscanf' with the variable argument list
     specified directly as for `vwscanf'.

   In GNU C, there is a special construct you can use to let the
compiler know that a function uses a `scanf'-style format string.  Then
it can check the number and types of arguments in each call to the
function, and warn you when they do not match the format string.  For
details, Note: Declaring Attributes of Functions
Attributes.