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       close - close a file descriptor


       #include <unistd.h>

       int close(int fd);


       close()  closes  a  file descriptor, so that it no longer refers to any
       file and may be reused.  Any record locks (see fcntl(2))  held  on  the
       file  it  was  associated  with,  and owned by the process, are removed
       (regardless of the file descriptor that was used to obtain the lock).

       If fd is the last file descriptor referring to the underlying open file
       description  (see open(2)), the resources associated with the open file
       description are freed; if the descriptor was the last  reference  to  a
       file which has been removed using unlink(2) the file is deleted.


       close()  returns  zero on success.  On error, -1 is returned, and errno
       is set appropriately.


       EBADF  fd isn’t a valid open file descriptor.

       EINTR  The close() call was interrupted by a signal; see signal(7).

       EIO    An I/O error occurred.


       SVr4, 4.3BSD, POSIX.1-2001.


       Not checking the return value of close() is a common  but  nevertheless
       serious  programming  error.   It  is  quite  possible that errors on a
       previous write(2) operation are first reported at  the  final  close().
       Not  checking the return value when closing the file may lead to silent
       loss of data.  This can especially be observed with NFS and  with  disk

       A   successful  close  does  not  guarantee  that  the  data  has  been
       successfully saved to disk, as the kernel defers  writes.   It  is  not
       common  for  a  file  system  to  flush  the buffers when the stream is
       closed.  If you need to be sure that the data is physically stored  use
       fsync(2).  (It will depend on the disk hardware at this point.)

       It  is  probably  unwise to close file descriptors while they may be in
       use by system calls in other threads in the same process.  Since a file
       descriptor  may  be reused, there are some obscure race conditions that
       may cause unintended side effects.


       fcntl(2), fsync(2), open(2), shutdown(2), unlink(2), fclose(3)


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