Format
#include <stdarg.h>
#include <stdio.h>
int vfscanf(FILE *stream, const char *format, va_list arg_ptr);Language Level: ANSI
Threadsafe: Yes.
Locale Sensitive: The behavior of this function might be affected by the LC_CTYPE and LC_NUMERIC categories of the current locale. The behavior might also be affected by the LC_UNI_CTYPE category of the current locale if LOCALETYPE(*LOCALEUCS2) or LOCALETYPE(*LOCALEUTF) is specified on the compilation command. This function is not available when LOCALETYPE(*CLD) is specified on the compilation command. For more information, see Understanding CCSIDs and Locales.
Description
The vfscanf() function reads data from a stream into locations specified by a variable number of arguments. The vfscanf() function works just like the fscanf()function, except that arg_ptr points to a list of arguments whose number can vary from call to call in the program. These arguments should be initialized by va_start for each call. In contrast, the fscanf() function can have a list of arguments, but the number of arguments in that list is fixed when you compile the program.
Each argument must be a pointer to a variable with a type that corresponds to a type specifier in format-string. The format has the same form and function as the format string for the scanf() function.
Return Value
The vfscanf() function returns the number of fields that were successfully converted and assigned. The return value does not include fields that were read but not assigned. The return value is EOF for an attempt to read at end-of-file if no conversion was performed. A return value of 0 means that no fields were assigned.
Example that uses vfscanf()
This example opens the file myfile for input, and then scans this file for a string, a long integer value, and a floating-point value.
#include <stdio.h>
#include <stdarg.h>
int vread(FILE *stream, char *fmt, ...)
{
int rc;
va_list arg_ptr;
va_start(arg_ptr, fmt);
rc = vfscanf(stream, fmt, arg_ptr);
va_end(arg_ptr);
return(rc);
}
#define MAX_LEN 80
int main(void)
{
FILE *stream;
long l;
float fp;
char s[MAX_LEN + 1];
char c;
stream = fopen("mylib/myfile", "r");
/* Put in various data. */
vread(stream, "%s", &s[0]);
vread(stream, "%ld", &l);
vread(stream, "%c", &c);
vread(stream, "%f", &fp);
printf("string = %s\n", s);
printf("long double = %ld\n", l);
printf("char = %c\n", c);
printf("float = %f\n", fp);
}
/*************** If myfile contains ************************
**************** abcdefghijklmnopqrstuvwxyz 343.2 ***********
********************** expected output is: *********************
string = abcdefghijklmnopqrstuvwxyz
long double = 343
char = .
float = 2.000000
*/Related Information