NAME
close - delete a descriptor
SYNOPSIS
#include <unistd.h>
int close(int d)
DESCRIPTION
The close call deletes a descriptor from the per-process
object reference table. If this is the last reference to
the underlying object, then it will be deactivated. For
example, on the last close of a file the current seek
pointer associated with the file is lost; on the last close
of a TCP/IP descriptor associated naming information and
queued data are discarded; on the last close of a file hold-
ing an advisory lock the lock is released (see further
fcntl(2)).
A close of all of a process's descriptors is automatic on
exit, but since there is a limit on the number of active
descriptors per process, close is necessary for programs
that deal with many descriptors.
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 descriptors can be rear-
ranged 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, flags)'' is provided, that can
be used to mark a descriptor "close on exec" by setting the
FD_CLOEXEC flag:
fcntl(d, F_SETFD, fcntl(d, F_GETFD) | FD_CLOEXEC);
RETURN VALUE
Upon successful completion, a value of 0 is returned. Oth-
erwise, a value of -1 is returned and the global integer
variable errno is set to indicate the error.
ERRORS
Close will fail if:
[EBADF] D is not an active descriptor.
SEE ALSO
open(2), pipe(2), execve(2), fcntl(2).