STDIO(3S) STDIO(3S)
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 effi-
cient 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 stan-
dard 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 defini-
tions. The functions and constants mentioned in sections
labeled 3S are declared in the include file and need no fur-
ther declaration. The constants, and the following `func-
tions' 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)
STDIO(3S) STDIO(3S)
has been attempted on an output (input) stream, or a FILE
pointer designates corrupt or otherwise unintelligible FILE
data.
BUGS
Buffering of output can prevent output data from being seen
until long after it is computed - perhaps never, as when an
abort occurs between buffer filling and flushing.
Buffering of input can cause a process to consume more input
than it actually uses. This can cause trouble across exec
(2) or system (3) calls.