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.
EINTR The close() call was interrupted by a signal.
EIO An I/O error occurred.
SVr4, SVID, POSIX, X/OPEN, BSD 4.3. SVr4 documents an additional ENOLINK
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. 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) 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)
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