1.\" Copyright (c) 1980, 1991, 1993, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)close.2 8.2 (Berkeley) 4/19/94 33.\" $FreeBSD$ 34.\" 35.Dd April 19, 1994 36.Dt CLOSE 2 37.Os BSD 4 38.Sh NAME 39.Nm close 40.Nd delete a descriptor 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.Fd #include <unistd.h> 45.Ft int 46.Fn close "int d" 47.Sh DESCRIPTION 48The 49.Fn close 50call deletes a descriptor from the per-process object 51reference table. 52If this is the last reference to the underlying object, the 53object will be deactivated. 54For example, on the last close of a file 55the current 56.Em seek 57pointer associated with the file is lost; 58on the last close of a 59.Xr socket 2 60associated naming information and queued data are discarded; 61on the last close of a file holding an advisory lock 62the lock is released (see further 63.Xr flock 2 ) . 64However, the semantics of System V and 65.St -p1003.1-88 66dictate that all 67.Xr fcntl 2 68advisory record locks associated with a file for a given process 69are removed when 70.Em any 71file descriptor for that file is closed by that process. 72.Pp 73When a process exits, 74all associated file descriptors are freed, but since there is 75a limit on active descriptors per processes, the 76.Fn close 77function call 78is useful when a large quantity of file descriptors are being handled. 79.Pp 80When a process forks (see 81.Xr fork 2 ) , 82all descriptors for the new child process reference the same 83objects as they did in the parent before the fork. 84If a new process is then to be run using 85.Xr execve 2 , 86the process would normally inherit these descriptors. Most 87of the descriptors can be rearranged with 88.Xr dup2 2 89or deleted with 90.Fn close 91before the 92.Xr execve 2 93is attempted, but if some of these descriptors will still 94be needed if the execve fails, it is necessary to arrange for them 95to be closed if the execve succeeds. 96For this reason, the call 97.Dq Li fcntl(d, F_SETFD, 1) 98is provided, 99which arranges that a descriptor will be closed after a successful 100execve; the call 101.Dq Li fcntl(d, F_SETFD, 0) 102restores the default, 103which is to not close the descriptor. 104.Sh IMPLEMENTATION NOTES 105.Pp 106In the non-threaded library 107.Fn close 108is implemented as the 109.Va close 110syscall. 111.Pp 112In the threaded library, the 113.Va close 114syscall is assembled to 115.Fn _thread_sys_close 116and 117.Fn close 118is implemented as a function which locks 119.Fa d 120for read and write, then calls 121.Fn _thread_sys_close . 122Before returning, 123.Fn close 124unlocks 125.Fa d . 126.Sh RETURN VALUES 127Upon successful completion, a value of 0 is returned. 128Otherwise, a value of -1 is returned and the global integer variable 129.Va errno 130is set to indicate the error. 131.Sh ERRORS 132.Fn Close 133will fail if: 134.Bl -tag -width Er 135.It Bq Er EBADF 136.Fa D 137is not an active descriptor. 138.It Bq Er EINTR 139An interrupt was received. 140.El 141.Sh SEE ALSO 142.Xr accept 2 , 143.Xr execve 2 , 144.Xr fcntl 2 , 145.Xr flock 2 , 146.Xr open 2 , 147.Xr pipe 2 , 148.Xr socket 2 , 149.Xr socketpair 2 150.Sh STANDARDS 151The 152.Fn close 153function call is expected to conform to 154.St -p1003.1-90 . 155.Sh HISTORY 156A 157.Fn close 158function call appeared in 159.At v7 . 160