NAME

stdio − standard buffered input/output package

SYNOPSIS

#include <stdio.h>

FILE ∗stdin;
FILE ∗stdout;
FILE ∗stderr;

DESCRIPTION

The functions described in Sections 3S constitute an efficient user-level buffering scheme.  The in-line macros getc and putc(3) handle characters quickly. The higher level routines gets, fgets, scanf, fscanf, fread, puts, fputs, printf, fprintf, fwrite all use getc and putc; they can be freely intermixed. 

A file with associated buffering is called a stream, and is declared to be a pointer to a defined type FILE.  Fopen(3) creates certain descriptive data for a stream and returns a pointer to designate the stream in all further transactions. There are three normally open streams with constant pointers declared in the include file and associated with the standard open files:

stdin standard input file

stdout standard output file

stderr standard error file

A constant ‘pointer’ NULL (0) designates no stream at all. 

An integer constant EOF (−1) is returned upon end of file or error by integer functions that deal with streams. 

Any routine that uses the standard input/output package must include the header file <stdio.h> of pertinent macro definitions.  The functions and constants mentioned in sections labeled 3S are declared in the include file and need no further declaration.  The constants, and the following ‘functions’ are implemented as macros; redeclaration of these names is perilous: getc, getchar, putc, putchar, feof, ferror, fileno.

SEE ALSO

open(2), close(2), read(2), write(2)

DIAGNOSTICS

The value EOF is returned uniformly to indicate that a FILE pointer has not been initialized with fopen, input (output) has been attempted on an output (input) stream, or a FILE pointer designates corrupt or otherwise unintelligible FILE data. 

7th Edition