NAME
stdio - standard buffered input/output package
SYNOPSIS
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
DESCRIPTION
The functions in the standard I/O library constitute a
user-level buffering scheme. The in-line macros getc and
putc(3) handle characters quickly. The higher level rou-
tines 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 stan-
dard 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 defini-
tions. The functions and constants mentioned in the stan-
dard I/O manual pages are declared in the include file and
need no further declaration. The constants, and the follow-
ing `functions' are implemented as macros; redeclaration of
these names is perilous: clearerr, getc, getchar, putc,
putchar, feof, ferror, fileno.
SEE ALSO
open(2), close(2), read(2), write(2), fclose(3), ferror(3),
fopen(3), fread(3), fseek(3), getc(3), gets(3), printf(3),
putc(3), puts(3), scanf(3), setbuf(3), ungetc(3).
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.
For purposes of efficiency, this implementation of the stan-
dard library has been changed to line buffer output to a
terminal by default and attempts to do this transparently by
flushing the output whenever a read(2) from the standard
input is necessary. This is almost always transparent, but
may cause confusion or malfunctioning of programs which use
standard i/o routines but use read(2) themselves to read
from the standard input.
In cases where a large amount of computation is done after
printing part of a line on an output terminal, it is neces-
sary to fflush(3) the standard output before going off and
computing so that the output will appear.
BUGS
The standard buffered functions do not interact well with
certain other library and system functions, especially fork
and abort.
LIST OF FUNCTIONS
Name Appears on Page Description
clearerr ferror(3) stream status inquiries
fclose fclose(3) close or flush a stream
fdopen fopen(3) open a stream
feof ferror(3) stream status inquiries
ferror ferror(3) stream status inquiries
fflush fclose(3) close or flush a stream
fgetc getc(3) get character or word from stream
fgets gets(3) get a string from a stream
fileno ferror(3) stream status inquiries
fopen fopen(3) open a stream
fprintf printf(3) formatted output conversion
fputc putc(3) put character or word on a stream
fputs puts(3) put a string on a stream
fread fread(3) buffered binary input/output
freopen fopen(3) open a stream
fscanf scanf(3) formatted input conversion
fseek fseek(3) reposition a stream
ftell fseek(3) reposition a stream
fwrite fread(3) buffered binary input/output
getc getc(3) get character or word from stream
getchar getc(3) get character or word from stream
gets gets(3) get a string from a stream
getw getc(3) get character or word from stream
printf printf(3) formatted output conversion
putc putc(3) put character or word on a stream
putchar putc(3) put character or word on a stream
puts puts(3) put a string on a stream
putw putc(3) put character or word on a stream
rewind fseek(3) reposition a stream
scanf scanf(3) formatted input conversion
setbuf setbuf(3) assign buffering to a stream
setvbuf setbuf(3) assign buffering to a stream
snprintf printf(3) formatted output conversion
sprintf printf(3) formatted output conversion
sscanf scanf(3) formatted input conversion
ungetc ungetc(3) push character back into input stream
vfprintf printf(3) formatted output conversion
vfscanf scanf(3) formatted input conversion
vprintf printf(3) formatted output conversion
vscanf scanf(3) formatted input conversion
vsnprintf printf(3) formatted output conversion
vsprintf printf(3) formatted output conversion
vsscanf scanf(3) formatted input conversion