close - close a file descriptor
int close(int fd);
close closes a file descriptor, so that it no longer
refers to any file and may be reused. Any locks 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 copy of a particular file descriptor the
resources associated with it 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, or -1 if an error occurred.
EBADF fd isn't a valid open file descriptor.
SVr4, SVID, POSIX, X/OPEN, BSD 4.3. SVr4 documents an
additional ENOLINK error condition.
Not checking the return value of close is a common but
nevertheless serious programming error. File system
implementations which use techniques as ``write-behind''
to increase performance may lead to write(2) succeeding,
although the data has not been written yet. The error
status may be reported at a later write operation, but it
is guaranteed to be reported on closing the file. Not
checking the return value when closing the file may lead
to silent loss of data. This can especially be observed
with NFS and disk quotas.
A successful close does not guarantee that the data has
been successfully saved to disk, as the kernel defers
writes. 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) or
sync(2), they will get you closer to that goal (it will
depend on the disk hardware at this point).
open(2), fcntl(2), shutdown(2), unlink(2), fclose(3)