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 38.Sh NAME 39.Nm close 40.Nd delete a descriptor 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft int 46.Fn close "int d" 47.Sh DESCRIPTION 48The 49.Fn close 50system call 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 77system 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. 87Most 88of the descriptors can be rearranged with 89.Xr dup2 2 90or deleted with 91.Fn close 92before the 93.Xr execve 2 94is attempted, but if some of these descriptors will still 95be needed if the execve fails, it is necessary to arrange for them 96to be closed if the execve succeeds. 97For this reason, the call 98.Dq Li fcntl(d, F_SETFD, FD_CLOEXEC) 99is provided, 100which arranges that a descriptor will be closed after a successful 101execve; the call 102.Dq Li fcntl(d, F_SETFD, 0) 103restores the default, 104which is to not close the descriptor. 105.Sh RETURN VALUES 106.Rv -std close 107.Sh ERRORS 108The 109.Fn close 110system call will fail if: 111.Bl -tag -width Er 112.It Bq Er EBADF 113The 114.Fa d 115argument 116is not an active descriptor. 117.It Bq Er EINTR 118An interrupt was received. 119.It Bq Er ENOSPC 120The underlying object did not fit, cached data was lost. 121.El 122.Sh SEE ALSO 123.Xr accept 2 , 124.Xr execve 2 , 125.Xr fcntl 2 , 126.Xr flock 2 , 127.Xr open 2 , 128.Xr pipe 2 , 129.Xr socket 2 , 130.Xr socketpair 2 131.Sh STANDARDS 132The 133.Fn close 134system call is expected to conform to 135.St -p1003.1-90 . 136.Sh HISTORY 137The 138.Fn close 139function appeared in 140.At v7 . 141