closes a file descriptor, so that it no longer refers to any file and
may be reused.
Any record locks (see
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).
is the last file descriptor referring to the underlying
open file description (see
the resources associated with the open file description are freed;
if the descriptor was the last reference to a file which has been
the file is deleted.
returns zero on success.
On error, -1 is returned, and
is set appropriately.
isn't a valid open file descriptor.
call was interrupted by a signal; see
An I/O error occurred.
SVr4, 4.3BSD, POSIX.1-2001.
Not checking the return value of
is a common but nevertheless
serious programming error.
It is quite possible that errors on a
operation are first reported at the final
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.
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
(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.