-=> Quoting Owen Kaluza to All <=-

Hello Owen,

OK> I am writing a library of functions to include in my programs
OK> with similar tasks to those in CONIO.H but using direct video
OK> output.

OK> I have struck problems in trying to write a version of printf().
OK> My idea was to write a function called dprintf() which accepted
OK> the arguments, used sprintf() to format them and store in a
OK> buffer and then output the resulting string to the screen.

OK> I don't know how the variable argument system works that
OK> printf() uses so I am unable to pass the values on to sprintf().

Check the routine below for ideas.  Instead of using vfprintf, you
would use vsprintf, which has identical syntax.

/* ************************************************* */

/*  FERRORF.C
**  Prints error message with printf() formatting syntax, then a colon,
**  then a message corressponding to the value of errno, then a newline.
**  Output is to filehandle.
**
**  Public Domain by Mark R. Devlin, free usage is permitted.
*/

#include 
#include 
#include 
#include 

int ferrorf(FILE *filehandle, const char *format, ...)
{
    int vfp, fp;
    va_list vargs;

    vfp = fp = 0;
    va_start(vargs, format);
    vfp = vfprintf(filehandle, format, vargs);
    va_end(vargs);
    fp = fprintf(filehandle, ": %s\n", sys_errlist[errno]);
    return ((vfp==EOF || fp==EOF) ? EOF : (vfp+fp));
}

/* ************************************************* */

I hope this gets you started in the right direction.  If you want to
know more about stdarg stuff, just ask.

Michael Stapleton of Graphic Bits.

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