CLOSE(2) manual page
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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 quota. Note that the return value should
only be used 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.
fcntl(2)
, fsync(2)
, open(2)
, shutdown(2)
, unlink(2)
, fclose(3)
This page is part of release 3.78 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/.
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