FCLOSE(3)                  POSIX Programmer's Manual                 FCLOSE(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
       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 .



IEEE/The Open Group                  2017                            FCLOSE(3)
