stdio
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 character-
istics 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 repositioned 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 ter-
mination. 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 read-
ing 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 out-
put 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 rou-
tines are automatically loaded as needed by the compilers
cc(1) and pc(1). The SYNOPSIS 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 defini-
tions 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, std-
out. Function versions of the macro functions feof, fer-
ror, clearerr, fileno, getc, getchar, putc, and putchar
exist and will be used if the macros definitions are
explicitly removed.
SEE ALSO
open(2), close(2), read(2), write(2)
BUGS
The standard buffered functions do not interact well with
certain other library and system functions, especially
vfork and abort. This may not be the case under Linux.
STANDARDS
The stdio library conforms to ANSI C3.159-1989 (``ANSI
C'').
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
fgetline
get a line from a 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
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