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.1‐2017 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 .