NAME
stderr, stdin, stdout - standard I/O streams
SYNOPSIS
#include <stdio.h>
extern FILE *stderr, *stdin, *stdout;
DESCRIPTION
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 ALSO
fclose() , feof() , ferror() , fileno() , fopen() , fread() , fseek() ,
getc() , gets() , popen() , printf() , putc() , puts() , read() ,
scanf() , setbuf() , setvbuf() , tmpfile() , ungetc() , vprintf() , the
Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>, <unistd.h>
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 .