NAME

       close - close a file descriptor

SYNOPSIS

       #include <unistd.h>

       int close(int fd);

DESCRIPTION

       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.

RETURN VALUE

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

ERRORS

       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.

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

NOTES

       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 quota.  Note that the return value should be used only for diagnostics.
       In particular close() should not be retried after an EINTR since this may cause a reused descriptor  from
       another thread to be closed.

       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 filesystem 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.

SEE ALSO

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

COLOPHON

       This page is part of release 4.04 of  the  Linux  man-pages  project.   A  description  of  the  project,
       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       http://www.kernel.org/doc/man-pages/.

Linux                                              2015-08-08                                           CLOSE(2)