text: CLOSE(2) BSD Programmer's Manual CLOSE(2)
  close - delete a descriptor
  #include <unistd.h> int close(int d);
  The; 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") process, the close() function call is useful when a large quantity of file descriptors are be- ing 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 image is to then be run using execve(2), the pro- cess would normally inherit these descriptors. Most of the descriptors can be rearranged with dup2(2) or deleted with close() 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 fcntl(d, F_SETFD, FD_CLOEXEC) is provided, which arranges that a descriptor will be closed after a successful execve(2); the call fcntl(d, F_SETFD, 0) re- stores), closefrom(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)
  close() conforms to IEEE Std 1003.1-1988 ("POSIX"). MirOS BSD #10-current April.