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

       fclose — close a stream

SYNOPSIS

       #include <stdio.h>

       int fclose(FILE *stream);

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.

       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.

RETURN VALUE

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

ERRORS

       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.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       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, Section 3.303, Process
       Termination), 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.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 2.5, Standard I/O Streams,  atexit(),  close(),  fmemopen(),  fopen(),  freopen(),
       getrlimit(), open_memstream(), ulimit()

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