CLOSE(2) BSD System Calls Manual CLOSE(2)
close -- delete a descriptor
The close() 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 exam-
ple, on the last close of a file the current seek pointer associated with the file is lost;
on the last close of a socket(2) associated naming information and queued data are dis-
carded; on the last close of a file holding an advisory lock the lock is released (see fur-
When a process exits, all associated file descriptors are freed, but since there is a limit
on active descriptors per processes, the close() function call is useful when a large quan-
tity of file descriptors are being handled.
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 is then to be run
using execve(2), the process would normally inherit these descriptors. Most of the descrip-
tors can be rearranged with dup2(2) or deleted with close() before the execve is attempted,
but if some of these descriptors will still be needed if the execve fails, it is necessary
to arrange for them to be closed if the execve succeeds. For this reason, the call
``fcntl(d, F_SETFD, 1)'' is provided, which arranges that a descriptor will be closed after
a successful execve; the call ``fcntl(d, 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:
[EBADF] D is not an active descriptor.
[EINTR] An interrupt was received.
accept(2), flock(2), open(2), pipe(2), socket(2), socketpair(2), execve(2), fcntl(2)
Close() conforms to IEEE Std 1003.1-1988 (``POSIX.1'').
4th Berkeley Distribution April 19, 1994 4th Berkeley Distribution