delete a descriptor
call deletes a descriptor from the per-process object reference table. If
this is the last reference to the underlying object, the object will be
deactivated. For example, on the last close of a file, the current
pointer associated with the file is lost; on the last close of a
socket(2), associated naming information and queued data are
discarded; and on the last close of a file holding an advisory lock, the
lock is released (see
flock(2)). However, the semantics of System V and
IEEE Std 1003.1-1988 (“POSIX.1”)
dictate that all
fcntl(2) advisory record locks associated with a file for a given
process are removed when
descriptor for that file is closed by that process.
When a process exits, all associated file descriptors
are freed, but since there is a limit on active descriptors per process, the
function call is useful when a large quantity of file descriptors are being
When a process forks (see
fork(2)), all descriptors for the new child process reference the
same objects as they did in the parent before the fork. If a new process
image is to then be run using
execve(2), the process would normally inherit these descriptors. Most
of the descriptors can be rearranged with
dup2(2) or deleted with
before the execve(2) is attempted, but since some of these descriptors
may still be needed should the
execve(2) fail, it is necessary to arrange for them to be closed when
the execve(2) succeeds. For this reason, the call
F_SETFD, FD_CLOEXEC) is
provided, which arranges that a descriptor will be closed after a successful
execve(2); the call
F_SETFD, 0) restores the
default, which is to not close the descriptor.
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and the global integer variable errno is set to indicate the error.
close() will fail if:
- d is not an active descriptor.
- An interrupt was received.
- An I/O error occurred while writing to the file system.
accept(2), closefrom(2), dup2(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)
close() conforms to IEEE
Std 1003.1-2008 (“POSIX.1”).
close() system call first appeared in
Version 1 AT&T UNIX.