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Full Discussion: Printf conversion specifiers
Top Forums Programming Printf conversion specifiers Post 302885102 by Corona688 on Thursday 23rd of January 2014 01:07:00 PM
Old 01-23-2014
You give printf and scanf identical command strings, but %* means something very different to printf and scanf. It means "print this type to [format] characters wide" in printf, and "don't store this value" in scanf.

Also, you are giving printf all the same arguments too. scanf needs &i because scanf needs i's location, not its contents -- but printf needs its contents, not its location!

So, my best guess at what happened is that printf's %d prints part of a memory address (since you are on a 64-bit system, and %d expects a 32-bit integer). Next, %*s tries to get a width, and gets the other half of that memory address -- a very, very high number! So it prints several billion leading spaces before it actually gets to the string.

Last edited by Corona688; 01-23-2014 at 02:15 PM..
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vprintf(3int)															     vprintf(3int)

Name
       vprintf, vfprintf, vsprintf - print formatted output of a varargs argument list

Syntax
       #include <stdio.h>
       #include <varargs.h>

       int vprintf ( format, ap )
       char *format;
       va list ap;

       int vfprintf ( stream, format, ap )
       FILE *stream;
       char *format;
       va list ap;

       int vsprintf ( s, format, ap )
       char *s, *format;
       va list ap;

Description
       The international functions and are similar to the standard I/O functions.

       Likewise,  the  vprintf functions are similar to the printf functions except they are called with an argument list as defined by instead of
       with a variable number of arguments.

       The international functions allow you to use the %digit$ conversion character in place of the % character  you  use  in	the  standard  I/O
       functions.   The digit is a decimal digit n from 1 to 9.  The international functions apply conversions to the nth argument in the argument
       list, rather than to the next unused argument.

       You can use the % conversion character in the international functions.  However, you cannot mix the % conversion character with the %digit$
       conversion character in a single call.

       You  can  indicate  a  field  width or precision by an asterisk (*) instead of a digit string in format strings containing the % conversion
       character. If you use an asterisk, you can supply an integer arg that specifies the field width or precision.  In format strings containing
       the  %digit$  conversion character, you can indicate field width or precision by the sequence *digit$.  You use a decimal digit from 1 to 9
       to indicate which argument contains an integer that specifies the field width or precision.

       The conversion characters and their meanings are identical to

       You must use each digit argument at least once.

Examples
       #include <stdio.h>
       #include <varargs.h>

       main()
       {
       char *function_name = "vpr";
       char *arg1 = "hello world";
       int arg2 = 2;
       char *arg3 = "study";

       char *i18nfmt = "%1$s %3$d
";

       test(function_name, i18nfmt, arg1, arg2, arg3);
       }

       test(va_alist)
       va_dcl
       {
       va_list args;
       char *fmt;
       char string[1024];

       va_start(args);

       (void)printf("function %s: ", va_arg(args, char *));

       fmt = va_arg(args, char *);

       (void)vprintf(fmt, args);

       va_end(args);
       }

See Also
       setlocale(3), scanf(3int), printf(3s), printf(3int), vprintf(3s), putc(3s), scanf(3s), stdio(3s), varargs(3)
       Guide to Developing International Software

																     vprintf(3int)
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