close(2) - NetBSD Manual Pages

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CLOSE(2)                  NetBSD Programmer's Manual                  CLOSE(2)


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 refer-
     ence 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 seek pointer associated with the file is lost; on the last close
     of a socket(2) associated naming information and queued data are discard-
     ed; on the last close of a file holding an advisory lock the lock is re-
     leased (see further flock(2)).

     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 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 is then to 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 close() before the execve is at-
     tempted, but if some of these descriptors will still be needed if the ex-
     ecve fails, it is necessary to arrange for them to be closed if the ex-
     ecve succeeds.  For this reason, the call ``fcntl(d, F_SETFD, 1)'' is
     provided, which arranges that a descriptor will be closed after a suc-
     cessful execve; the call ``fcntl(d, F_SETFD, 0)'' restores the default,
     which is to not close the descriptor.


RETURN VALUES

     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 indi-
     cate the error.


ERRORS

     Close() will fail if:

     [EBADF]       D is not an active descriptor.

     [EINTR]       An interrupt was received.


SEE ALSO

     accept(2),  flock(2),  open(2),  pipe(2),  socket(2),  socketpair(2),
     execve(2),  fcntl(2)


STANDARDS

     The close() function conforms to IEEE Std1003.1-1990 (``POSIX'').

4th Berkeley Distribution       April 19, 1994                               1