This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       Since after the call to fclose() any use of stream results in undefined behavior, fclose() should not  be
       used  on stdin, stdout, or stderr except immediately before process termination (see the Base Definitions
       volume of POSIX.1‐2017, Section3.303, ProcessTermination), so as to avoid triggering undefined behavior
       in other standard interfaces that rely on these streams. If there are any atexit() handlers registered by
       the application, such a call to fclose() should not occur until  the  last  handler  is  finishing.  Once
       fclose() has been used to close stdin, stdout, or stderr, there is no standard way to reopen any of these
       streams.

       Use  of  freopen() to change stdin, stdout, or stderr instead of closing them avoids the danger of a file
       unexpectedly being opened as  one  of  the  special  file  descriptors  STDIN_FILENO,  STDOUT_FILENO,  or
       STDERR_FILENO at a later time in the application.

       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                                        FCLOSE(3POSIX)

       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.

       The  fclose()  function shall cause the stream pointed to by stream to be flushed and the associated file
       to be closed. Any unwritten buffered data for the stream  shall  be  written  to  the  file;  any  unread
       buffered  data  shall  be  discarded. Whether or not the call succeeds, the stream shall be disassociated
       from the file and any buffer set by the setbuf() or setvbuf() function shall be  disassociated  from  the
       stream. If the associated buffer was automatically allocated, it shall be deallocated.

       If  the  file  is  not  already  at  EOF,  and the file is one capable of seeking, the file offset of the
       underlying open file description shall be set to the file position of the stream if  the  stream  is  the
       active handle to the underlying file description.

       The  fclose()  function  shall  mark  for  update  the last data modification and last file status change
       timestamps of the underlying file, if the stream was writable, and if buffered data remains that has  not
       yet been written to the file. The fclose() function shall perform the equivalent of a close() on the file
       descriptor that is associated with the stream pointed to by stream.

       After the call to fclose(), any use of stream results in undefined behavior.

       The fclose() function shall fail if:

       EAGAIN The O_NONBLOCK flag is set for the file descriptor underlying  stream  and  the  thread  would  be
              delayed in the write operation.

       EBADF  The file descriptor underlying stream is not valid.

       EFBIG  An attempt was made to write a file that exceeds the maximum file size.

       EFBIG  An attempt was made to write a file that exceeds the file size limit of the process.

       EFBIG  The  file  is  a  regular  file  and  an attempt was made to write at or beyond the offset maximum
              associated with the corresponding stream.

       EINTR  The fclose() function was interrupted by a signal.

       EIO    The process is a member of a background process group  attempting  to  write  to  its  controlling
              terminal,  TOSTOP  is set, the calling thread is not blocking SIGTTOU, the process is not ignoring
              SIGTTOU, and the process group of the process is orphaned.  This error may also be returned  under
              implementation-defined conditions.

       ENOMEM The underlying stream was created by open_memstream() or open_wmemstream() and insufficient memory
              is available.

       ENOSPC There  was  no free space remaining on the device containing the file or in the buffer used by the
              fmemopen() function.

       EPIPE  An attempt is made to write to a pipe or FIFO that is not open  for  reading  by  any  process.  A
              SIGPIPE signal shall also be sent to the thread.

       The fclose() function may fail if:

       ENXIO  A  request  was  made  of a nonexistent device, or the request was outside the capabilities of the
              device.

       Thefollowingsectionsareinformative.

       None.

       None.

       fclose — close a stream

       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.

       None.

       Upon  successful  completion,  fclose()  shall  return 0; otherwise, it shall return EOF and set errno to
       indicate the error.

Section2.5,  StandardI/OStreams,  atexit(),  close(),  fmemopen(), fopen(), freopen(), getrlimit(),
       open_memstream(), ulimit()

       The Base Definitions volume of POSIX.1‐2017, <stdio.h>

       #include <stdio.h>

       int fclose(FILE *stream);