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Synopsis:
    #include <stdio.h>
    #include <stdarg.h>
    int vfprintf( FILE *fp,
                  const char *format,
                  va_list arg );

Description:
    The vfprintf function writes output to the file pointed to by fp under
    control of the argument format.  The format string is described under
    the description of the  printf function.  The vfprintf function is
    equivalent to the  fprintf function, with the variable argument list
    replaced with arg, which has been initialized by the  va_start macro.

Returns:
    The vfprintf function returns the number of characters written, or a
    negative value if an output error occurred.  When an error has occurred,
     errno contains a value indicating the type of error that has been
    detected.

See Also:
    _bprintf, cprintf, fprintf, printf, sprintf, va_arg, va_end, va_start,
    _vbprintf, vcprintf, vprintf, vsprintf

Example:
    #include <stdio.h>
    #include <stdarg.h>

    FILE *LogFile;

    /* a general error routine */

    void errmsg( char *format, ... )
      {
        va_list arglist;

        fprintf( stderr, "Error: " );
        va_start( arglist, format );
        vfprintf( stderr, format, arglist );
        va_end( arglist );
        if( LogFile != NULL ) {
          fprintf( LogFile, "Error: " );
          va_start( arglist, format );
          vfprintf( LogFile, format, arglist );
          va_end( arglist );
        }
      }

    void main()
      {
        LogFile = fopen( "error.log", "w" );
        errmsg( "%s %d %s", "Failed", 100, "times" );
      }

Classification:
    ANSI

Systems:
    All