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@(#)close.2 8.2 (Berkeley) 4/19/94
$Id$
.Dd April 19, 1994 .Dt CLOSE 2 .Os BSD 4 .Sh NAME .Nm close .Nd delete a descriptor .Sh SYNOPSIS .Fd #include <unistd.h> .Ft int .Fn close "int d" .Sh DESCRIPTION The .Fn 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 example, on the last close of a file the current .Em seek pointer associated with the file is lost; on the last close of a .Xr socket 2 associated naming information and queued data are discarded; on the last close of a file holding an advisory lock the lock is released (see further .Xr flock 2 ) .
p When a process exits, all associated file descriptors are freed, but since there is a limit on active descriptors per processes, the .Fn close function call is useful when a large quantity of file descriptors are being handled.
p When a process forks (see .Xr 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 .Xr execve 2 , the process would normally inherit these descriptors. Most of the descriptors can be rearranged with .Xr dup2 2 or deleted with .Fn close before the .Xr execve 2 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 .Dq Li fcntl(d, F_SETFD, 1) is provided, which arranges that a descriptor will be closed after a successful execve; the call .Dq Li fcntl(d, F_SETFD, 0) restores the default, which is to not close the descriptor. .Sh IMPLEMENTATION NOTES
p In the non-threaded library .Fn close is implemented as the .Va close syscall.
p In the threaded library, the .Va close syscall is assembled to .Fn _thread_sys_close and .Fn close is implemented as a function which locks .Va d for read and write, then calls .Fn _thread_sys_close . Before returning, .Fn close unlocks .Va d . .Sh RETURN VALUES Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and the global integer variable .Va errno is set to indicate the error. .Sh ERRORS .Fn Close will fail if: l -tag -width Er t Bq Er EBADF .Fa D is not an active descriptor. t Bq Er EINTR An interrupt was received. .El .Sh SEE ALSO .Xr accept 2 , .Xr flock 2 , .Xr open 2 , .Xr pipe 2 , .Xr socket 2 , .Xr socketpair 2 , .Xr execve 2 , .Xr fcntl 2 .Sh STANDARDS .Fn Close conforms to IEEE Std 1003.1-1988
q Dq Tn POSIX . .Sh HISTORY A .Fn close function call appeared in .At v7 .