NAME

stdio − standard buffered input/output package

SYNOPSIS

#include <stdio.h>

FILE ∗stdin;
FILE ∗stdout;
FILE ∗stderr;

DESCRIPTION

The functions described in section 3S constitute a user-level buffering scheme.  The in-line macros getc and putc(3S) 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(3S) 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 functions 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), fread(3S), fseek(3S), f∗(3S)

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 standard 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 necessary to fflush(3S) 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 vfork and abort. 

LIST OF FUNCTIONS

NameAppears on PageDescription
clearerrferror.3sstream status inquiries
fclosefclose.3sclose or flush a stream
fdopenfopen.3sopen a stream
feofferror.3sstream status inquiries
ferrorferror.3sstream status inquiries
fflushfclose.3sclose or flush a stream
fgetcgetc.3sget character or word from stream
fgetsgets.3sget a string from a stream
filenoferror.3sstream status inquiries
fopenfopen.3sopen a stream
fprintfprintf.3sformatted output conversion
fputcputc.3sput character or word on a stream
fputsputs.3sput a string on a stream
freadfread.3sbuffered binary input/output
freopenfopen.3sopen a stream
fscanfscanf.3sformatted input conversion
fseekfseek.3sreposition a stream
ftellfseek.3sreposition a stream
fwritefread.3sbuffered binary input/output
getcgetc.3sget character or word from stream
getchargetc.3sget character or word from stream
getsgets.3sget a string from a stream
getwgetc.3sget character or word from stream
printfprintf.3sformatted output conversion
putcputc.3sput character or word on a stream
putcharputc.3sput character or word on a stream
putsputs.3sput a string on a stream
putwputc.3sput character or word on a stream
rewindfseek.3sreposition a stream
scanfscanf.3sformatted input conversion
setbufsetbuf.3sassign buffering to a stream
setbuffersetbuf.3sassign buffering to a stream
setlinebufsetbuf.3sassign buffering to a stream
sprintfprintf.3sformatted output conversion
sscanfscanf.3sformatted input conversion
ungetcungetc.3spush character back into input stream

4th Berkeley Distribution  —  May 13, 1986