4.4BSD/usr/src/lib/libc/stdio/stdio.3
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.\" @(#)stdio.3 8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt STDIO 3
.Os BSD 4
.Sh NAME
.Nm stdio
.Nd standard input/output library functions
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Fd FILE *stdin;
.Fd FILE *stdout;
.Fd FILE *stderr;
.Sh DESCRIPTION
The standard
.Tn I/O
library provides a simple and efficient buffered stream
.Tn I/O
interface.
Input and ouput is mapped into logical data streams
and the physical
.Tn I/O
characteristics are concealed. The functions and macros are listed
below; more information is available from the individual man pages.
.Pp
A stream is associated with an external file (which may be a physical
device) by
.Em 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
.Em file position indicator
associated with the stream is positioned at the start of the file (byte
zero), unless the file is opened with appened 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
.Xr fgetc 3
function; all ouput takes place as if all characters were
read by successive calls to the
.Xr fputc 3
function.
.Pp
A file is disassociated from a stream by
.Em closing
the file.
Ouput streams are flushed (any unwritten buffer contents are transfered
to the host environment) before the stream is disassociated from the file.
The value of a pointer to a
.Dv FILE
object is indeterminate after a file is closed (garbage).
.Pp
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
.Xr 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
.Xr abort 3
do not bother about closing files properly.
.Pp
At program startup, three text streams are predefined and need not be
opened explicitly
\(em
.Em standard input
(for reading converntional input),
\(em
.Em standard output
(for writing converntional input),
and
.Em standard error
(for writing diagnostic output).
These streams are abbreviated
.Em stdin , stdout
and
.Em 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.
.Pp
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
.Xr fflush 3
the standard output before going off and computing so that the output
will appear.
.Pp
The
.Nm stdio
library is a part of the library
.Xr libc
and routines are automatically loaded as needed by the compilers
.Xr cc 1
and
.Xr pc 1 .
The
.Tn 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.
.Pp
The following are defined as macros;
these names may not be re-used
without first removing their current definitions with
.Dv #undef :
.Dv BUFSIZ ,
.Dv EOF ,
.Dv FILENAME_MAX ,
.DV FOPEN_MAX ,
.Dv L_cuserid ,
.Dv L_ctermid ,
.Dv L_tmpnam,
.Dv NULL ,
.Dv SEEK_END ,
.Dv SEEK_SET ,
.Dv SEE_CUR ,
.Dv TMP_MAX ,
.Dv clearerr ,
.Dv feof ,
.Dv ferror ,
.Dv fileno ,
.Dv fropen ,
.Dv fwopen ,
.Dv getc ,
.Dv getchar ,
.Dv putc ,
.Dv putchar ,
.Dv stderr ,
.Dv stdin ,
.Dv stdout .
Function versions of the macro functions
.Xr feof ,
.Xr ferror ,
.Xr clearerr ,
.Xr fileno ,
.Xr getc ,
.Xr getchar ,
.Xr putc ,
and
.Xr putchar
exist and will be used if the macros
definitions are explicitly removed.
.Sh SEE ALSO
.Xr open 2 ,
.Xr close 2 ,
.Xr read 2 ,
.Xr write 2
.Sh BUGS
The standard buffered functions do not interact well with certain other
library and system functions, especially
.Xr vfork
and
.Xr abort .
.Sh STANDARDS
The
.Nm stdio
library conforms to
.St -ansiC .
.Sh LIST OF FUNCTIONS
.Bl -column "Description"
.Sy 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
funopen open a stream
fwopen open 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
snprintf formatted output conversion
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
vsnprintf formatted output conversion
vsprintf formatted output conversion
vsscanf input format conversion
.El