stdio(3s)
NAME
stdio − standard buffered input/output package
SYNTAX
#include <stdio.h>
FILE *stdin, *stdout, *stderr;
DESCRIPTION
The subroutines constitute an efficient user-level buffering scheme. The in-line macros getc and putc(3s) 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. The fopen subroutine 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 .
DIAGNOSTICS
The value EOF is returned uniformly to indicate that either a FILE pointer has not been initialized with fopen, I/O has been attempted on an I/O stream, or a FILE pointer designates corrupt or otherwise unintelligible FILE data.