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 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 func-
tions 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.
STDIO(3S)
Check Out this Related Man Page
STDIO(3) Linux Programmer's Manual STDIO(3)
NAME
stdio - standard input/output library functions
SYNOPSIS
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
DESCRIPTION
The standard I/O library provides a simple and efficient buffered stream I/O interface. Input and output is mapped into logical data
streams and the physical I/O characteristics are concealed. The functions and macros are listed below; more information is available from
the individual man pages.
A stream is associated with an external file (which may be a physical device) by opening a file, which may involve creating a new file.
Creating an existing file causes its former contents to be discarded. If a file can support positioning requests (such as a disk file, as
opposed to a terminal) then a file position indicator associated with the stream is positioned at the start of the file (byte zero), unless
the file is opened with append mode. If append mode is used, the position indicator will be placed the end-of-file. The position indicator
is maintained by subsequent reads, writes and positioning requests. All input occurs as if the characters were read by successive calls to
the fgetc(3) function; all output takes place as if all characters were read by successive calls to the fputc(3) function.
A file is disassociated from a stream by closing the file. Output streams are flushed (any unwritten buffer contents are transferred to
the host environment) before the stream is disassociated from the file. The value of a pointer to a FILE object is indeterminate after a
file is closed (garbage).
A file may be subsequently reopened, by the same or another program execution, and its contents reclaimed or modified (if it can be reposi-
tioned at the start). If the main function returns to its original caller, or the exit(3) function is called, all open files are closed
(hence all output streams are flushed) before program termination. Other methods of program termination, such as abort(3) do not bother
about closing files properly.
At program startup, three text streams are predefined and need not be opened explicitly -- standard input (for reading conventional input),
-- standard output (for writing conventional input), and standard error (for writing diagnostic output). These streams are abbreviated
stdin,stdout and stderr. When opened, the standard error stream is not fully buffered; the standard input and output streams are fully
buffered if and only if the streams do not to refer to an interactive device.
Output streams that refer to terminal devices are always line buffered by default; pending output to such streams is written automatically
whenever an input stream that refers to a terminal device is read. In cases where a large amount of computation is done after printing
part of a line on an output terminal, it is necessary to fflush(3) the standard output before going off and computing so that the output
will appear.
The stdio library is a part of the library libc and routines are automatically loaded as needed by the compilers cc(1) and pc(1). The SYN-
OPSIS sections of the following manual pages indicate which include files are to be used, what the compiler declaration for the function
looks like and which external variables are of interest.
The following are defined as macros; these names may not be re-used without first removing their current definitions with #undef: BUFSIZ,
EOF, FILENAME_MAX, FOPEN_MAX, L_cuserid, L_ctermid, L_tmpnam, NULL, SEEK_END, SEEK_SET, SEE_CUR, TMP_MAX, clearerr, feof, ferror, fileno,
fropen, fwopen, getc, getchar, putc, putchar, stderr, stdin, stdout. Function versions of the macro functions feof, ferror, clearerr,
fileno, getc, getchar, putc, and putchar exist and will be used if the macros definitions are explicitly removed.
LIST OF FUNCTIONS
Function Description
clearerr check and reset stream status
fclose close a stream
fdopen stream open functions
feof check and reset stream status
ferror check and reset stream status
fflush flush a stream
fgetc get next character or word from input stream
fgetpos reposition a stream
fgets get a line from a stream
fileno check and reset stream status
fopen stream open functions
fprintf formatted output conversion
fpurge flush a stream
fputc output a character or word to a stream
fputs output a line to a stream
fread binary stream input/output
freopen stream open functions
fropen open a stream
fscanf input format conversion
fseek reposition a stream
fsetpos reposition a stream
ftell reposition a stream
fwrite binary stream input/output
getc get next character or word from input stream
getchar get next character or word from input stream
gets get a line from a stream
getw get next character or word from input stream
mktemp make temporary file name (unique)
perror system error messages
printf formatted output conversion
putc output a character or word to a stream
putchar output a character or word to a stream
puts output a line to a stream
putw output a character or word to a stream
remove remove directory entry
rewind reposition a stream
scanf input format conversion
setbuf stream buffering operations
setbuffer stream buffering operations
setlinebuf
stream buffering operations
setvbuf stream buffering operations
sprintf formatted output conversion
sscanf input format conversion
strerror system error messages
sys_errlist
system error messages
sys_nerr system error messages
tempnam temporary file routines
tmpfile temporary file routines
tmpnam temporary file routines
ungetc un-get character from input stream
vfprintf formatted output conversion
vfscanf input format conversion
vprintf formatted output conversion
vscanf input format conversion
vsprintf formatted output conversion
vsscanf input format conversion
CONFORMING TO
The stdio library conforms to ANSI X3.159-1989 (``ANSI C'').
SEE ALSO
open(2), close(2), read(2), write(2), stdout(3)
2001-12-26 STDIO(3)