Node:Variable Arguments Input,
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Variable Arguments Input Functions
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.  See 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.
| int vscanf (const char *template, va_list ap) | Function | 
| This function is similar to scanf, but instead of taking
a variable number of arguments directly, it takes an argument list
pointer ap of typeva_list(see Variadic Functions). | 
| int vwscanf (const wchar_t *template, va_list ap) | Function | 
| This function is similar to wscanf, but instead of taking
a variable number of arguments directly, it takes an argument list
pointer ap of typeva_list(see Variadic Functions). | 
| int vfscanf (FILE *stream, const char *template, va_list ap) | Function | 
| This is the equivalent of fscanfwith the variable argument list
specified directly as forvscanf. | 
| int vfwscanf (FILE *stream, const wchar_t *template, va_list ap) | Function | 
| This is the equivalent of fwscanfwith the variable argument list
specified directly as forvwscanf. | 
| int vsscanf (const char *s, const char *template, va_list ap) | Function | 
| This is the equivalent of sscanfwith the variable argument list
specified directly as forvscanf. | 
| int vswscanf (const wchar_t *s, const wchar_t *template, va_list ap) | Function | 
| This is the equivalent of swscanfwith the variable argument list
specified directly as forvwscanf. | 
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, See Declaring Attributes of Functions.