FILE *stdin, *stdiout, *stderr;
A file with associated buffering is called a stream and is declared to be a pointer to a defined type FILE. fopen(3P) creates certain descriptive data for a stream and returns a pointer to designate the stream in all furthur transactions. Normally, there are 3 open streams with constant pointers declared in the include file and associated with the standard open files:
A constant "pointer" NULL (0) designates the null stream.
An integer constant EOF (-1) is returned upon end-of-file or error by most integer functions that deal with streams (see the individual descriptions for details).
Any program that uses this package must inculde the header file of pertinent macro definitions, as follows:
#include <stdio_p.h>The functions and constants mentioned in the entries of this manual are declared in that include file and need no further declaration. The constants and the folowing functions are implemented as macros (redeclaration of these names is perilous): getc, getchar, putc, putchar, feof, ferror, and fileno.