STDIN(3)                   POSIX Programmer's Manual                  STDIN(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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.1-2017
       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 ALSO
       fclose(), 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.1-2017, <stdio.h>, <unistd.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             STDIN(3)
