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4.75 viscanf, vfiscanf, vsiscanf—format argument list

Synopsis 

     #include <stdio.h>
     #include <stdarg.h>
     int viscanf(const char *fmt, va_list list);
     int vfiscanf(FILE *fp, const char *fmt, va_list list);
     int vsiscanf(const char *str, const char *fmt, va_list list);
     
     int _viscanf_r(struct _reent *reent, const char *fmt,
         va_list list);
     int _vfiscanf_r(struct _reent *reent, FILE *fp, const char *fmt,
         va_list list);
     int _vsiscanf_r(struct _reent *reent, const char *str,
         const char *fmt, va_list list);

Description
viscanf, vfiscanf, and vsiscanf are (respectively) variants of iscanf, fiscanf, and siscanf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments.
Returns
The return values are consistent with the corresponding functions: viscanf returns the number of input fields successfully scanned, converted, and stored; the return value does not include scanned fields which were not stored.

If viscanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

The routines _viscanf_r, _vfiscanf_f, and _vsiscanf_r are reentrant versions which take an additional first parameter which points to the reentrancy structure.
Portability
These are newlib extensions.

Supporting OS subroutines required: