stdio - standard buffered input/output package
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 sec-
tions 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.
open(2), close(2), read(2), write(2)
The value EOF is returned uniformly to indicate that a FILE pointer has not been initial-
ized with fopen, input (output) has been attempted on an output (input) stream, or a FILE
pointer designates corrupt or otherwise unintelligible FILE data.