.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "STDIN" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" stdin 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
stderr, stdin, stdout \- standard I/O streams
.SH SYNOPSIS
.LP
\fB#include <stdio.h>
.br
.sp
extern FILE *stderr, *stdin, *stdout;
.br
\fP
.SH DESCRIPTION
.LP
A file with associated buffering is called a \fIstream\fP and is declared
to be a pointer to a defined type \fBFILE\fP. The \fIfopen\fP() function
shall create certain descriptive data for a stream and return a pointer
to designate the stream in all further transactions. Normally, there
are three open streams with constant pointers declared in the
\fI<stdio.h>\fP header and associated with the standard open files.
.LP
At program start-up, three streams shall be predefined and need not
be opened explicitly: \fIstandard input\fP (for reading
conventional input), \fIstandard output\fP (for writing conventional
output), and \fIstandard error\fP (for writing diagnostic
output). When opened, the standard error stream is not fully buffered;
the standard input and standard output streams are fully
buffered if and only if the stream can be determined not to refer
to an interactive device.
.LP
The
following symbolic values in \fI<unistd.h>\fP define the file descriptors
that shall
be associated with the C-language \fIstdin\fP, \fIstdout\fP, and \fIstderr\fP
when the application is started:
.TP 7
STDIN_FILENO
Standard input value, \fIstdin\fP. Its value is 0.
.TP 7
STDOUT_FILENO
Standard output value, \fIstdout\fP. Its value is 1.
.TP 7
STDERR_FILENO
Standard error value, \fIstderr\fP. Its value is 2.
.sp
.LP
The \fIstderr\fP stream is expected to be open for reading and writing.
.SH RETURN VALUE
.LP
None.
.SH ERRORS
.LP
No errors are defined.
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIfclose\fP(), \fIfeof\fP(), \fIferror\fP(),
\fIfileno\fP(), \fIfopen\fP(), \fIfread\fP(), \fIfseek\fP(), \fIgetc\fP(),
\fIgets\fP(), \fIpopen\fP(), \fIprintf\fP(), \fIputc\fP(), \fIputs\fP(),
\fIread\fP(), \fIscanf\fP(), \fIsetbuf\fP(), \fIsetvbuf\fP(),
\fItmpfile\fP(), \fIungetc\fP(), \fIvprintf\fP(), the Base Definitions
volume of
IEEE\ Std\ 1003.1-2001, \fI<stdio.h>\fP, \fI<unistd.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .