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### 4.52 `vscanf`, `vfscanf`, `vsscanf`—format argument list

Synopsis

         #include <stdio.h>
         #include <stdarg.h>
         int vscanf(const char *fmt, va_list list);
         int vfscanf(FILE *fp, const char *fmt, va_list list);
         int vsscanf(const char *str, const char *fmt, va_list list);

         int _vscanf_r(struct _reent *reent, const char *fmt,
             va_list list);
         int _vfscanf_r(struct _reent *reent, FILE *fp, const char *fmt,
             va_list list);
         int _vsscanf_r(struct _reent *reent, const char *str,
             const char *fmt, va_list list);

Description
`vscanf`, `vfscanf`, and `vsscanf` are (respectively) variants of `scanf`, `fscanf`, and `sscanf`. 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: `vscanf` returns the number of input fields successfully scanned, converted, and stored; the return value does not include scanned fields which were not stored.

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

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

The routines `_vscanf_r`, `_vfscanf_f`, and `_vsscanf_r` are reentrant versions which take an additional first parameter which points to the reentrancy structure.

Portability
These are GNU extensions.

Supporting OS subroutines required: