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The C and C++ Libraries

printf family

The

printf

family consists of

_printf()

printf()

_fprintf()

fprintf()

vprintf()

and

vfprintf()

. All these functions use

__FILE

opaquely and depend only on the

functions

fputc()

and

ferror()

. The functions

_printf()

and

_fprintf()

are identical to

printf()

and

fprintf()

except that they cannot format floating-point values.

The standard output functions of the form

_printf(...)

are equivalent to:

fprintf(& __stdout, ...)

where

__stdout

has type

__FILE

scanf family

The

scanf()

family consists of

scanf()

and

fscanf()

. These functions depend only on

the functions

fgetc()

__FILE

, and

__backspace()

The standard input form

scanf(...)

is equivalent to:

fscanf(& __stdin, ...)

where

__stdin

has type

__FILE

fwrite(), fputs, and puts

If you define your own version of

__FILE

, and your own

fputc()

and

ferror()

functions

and the

__stdout

object, you can use all of the

printf()

family,

fwrite()

fputs()

, and

puts()

unchanged from the library. Example 4-19 shows how to do this. Consider

modifying the system routines if you require real file handling.

Example 4-19 printf() and __FILE

#include <stdio.h>

struct __FILE {

int handle;

/* Whatever you need here (if the only files you are using

is the stdoutput using printf for debugging, no file

handling is required) */

};

FILE __stdout;

int fputc(int ch, FILE *f)

{

/* Your implementation of fputc */

return ch;

}

int ferror(FILE *f)

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