STDIN(3P) POSIX Programmer's Manual STDIN(3P)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.
NAME
stderr, stdin, stdout — standard I/O streams
SYNOPSIS
#include <stdio.h>
extern FILE *stderr, *stdin, *stdout;
DESCRIPTION
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1‐2008
defers to the ISO C standard.
A file with associated buffering is called a stream and is declared to
be a pointer to a defined type FILE. The fopen() 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 <stdio.h> header and
associated with the standard open files.
At program start-up, three streams shall be predefined and need not be
opened explicitly: standard input (for reading conventional input),
standard output (for writing conventional output), and standard error
(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.
The following symbolic values in <unistd.h> define the file descriptors
that shall be associated with the C-language stdin, stdout, and stderr
when the application is started:
STDIN_FILENO Standard input value, stdin. Its value is 0.
STDOUT_FILENO Standard output value, stdout. Its value is 1.
STDERR_FILENO Standard error value, stderr. Its value is 2.
The stderr stream is expected to be open for reading and writing.
RETURN VALUE
None.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOfclose(), feof(), ferror(), fileno(), fopen(), fprintf(), fread(),
fscanf(), fseek(), getc(), gets(), popen(), putc(), puts(), read(),
setbuf(), setvbuf(), tmpfile(), ungetc(), vfprintf()
The Base Definitions volume of POSIX.1‐2008, <stdio.h>, <unistd.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 STDIN(3P)
