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,
it is unspecified whether the position indicator will be placed at the
start or the end of the 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 written 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 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
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 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
return the integer descriptor of the argument stream
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'').
