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 characteris-
tics 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 creat-
ing 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 charac-
ters 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 (gar-
bage).
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 func-
tion 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 diag-
nostic 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.
SEE ALSO
open(2), close(2), read(2), write(2), stdout(3)
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