C in a Nutshell

Name

vfscanf, vscanf, vsscanf

Synopsis

Reads formatted data using a variable argument list

#include <stdio.h>
#include <stdarg.h>
intvfscanf( FILE * restrict fp, const char * restrict format,
             va_list argptr );
int vscanf( const char * restrict format, va_list argptr );
int vsscanf( char * restrict buffer, const char * restrict format,
             va_list argptr );

The functions vfscanf(), vscanf(), and vsscanf() work in the same way as fscanf(), scanf(), and sscanf(), respectively, except that their final argument, argptr, is a variable-argument list object with type va_list. The program must initialize this object by calling the va_start macro before calling the vfscanf(), vscanf(), or vsscanf() function, and must call the va_end() macro after the function returns. Because these functions use the va_arg() macro internally to advance the pointer through the argument list, its value is indeterminate after the vfscanf(), vscanf(), or vsscanf() function call has returned.

Tip

The va_start(), va_arg(), and va_end() macros and the type va_list are declared in the header file stdarg.h.

Like the fscanf(), scanf(), and sscanf() functions, vfscanf(), vscanf(), and vsscanf() return the number of input items that have been assigned to variables referenced by elements of the argument list.

Example

typedef struct { char lastname[20]; char firstname[20]; int dob_month; int dob_day; int dob_year; } person; person employee; int read_person( char *lname, char *fname, ... ) // As variable arguments (...) use NULL // ...