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vfprintf, vfwprintf

Header File

stdio.h

Category

Input/output Routines

Prototype

int vfprintf(FILE *stream, const char *format, va_list arglist);

int vfwprintf(FILE *stream, const wchar_t *format, va_list arglist);

Description

Writes formatted output to a stream.

The v...printf functions are known as alternate entry points for the ...printf functions. They behave exactly like their ...printf counterparts, but they accept a pointer to a list of arguments instead of an argument list.

For details on format specifiers, see Printf Format Specifiers.

vfprintf accepts a pointer to a series of arguments, applies to each argument a format specifier contained in the format string pointed to by format, and outputs the formatted data to a stream. There must be the same number of format specifiers as arguments.

Return Value

On success, vfprintf returns the number of bytes output.

On error, it returns EOF.

Example

Copy Code

    #include <stdio.h>
    #include <stdlib.h>
    #include <stdarg.h>
    FILE *fp;
    int vfpf(char *fmt, ...)
    {
       va_list argptr;
       int cnt;
       va_start(argptr, fmt);
       cnt = vfprintf(fp, fmt, argptr);
       va_end(argptr);
       return(cnt);
    }
    int main(void)
    {
       int inumber = 30;
       float fnumber = 90.0;
       char string[4] = "abc";
       fp = tmpfile();
       if (fp == NULL)
       {
          perror("tmpfile() call");
          exit(1);
       }
       vfpf("%d %f %s", inumber, fnumber, string);
       rewind(fp);
       fscanf(fp,"%d %f %s", &inumber, &fnumber, string);
       printf("%d %f %s\n", inumber, fnumber, string);
       fclose(fp);
       return 0;
    }

Portability

| POSIX | Win32 | ANSI C | ANSI C++
vfprintf | + | + | + | +
vfwprintf |  | + | + | +

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