1.\" $NetBSD: close.2,v 1.5 1995/02/27 12:32:14 cgd Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993, 1994 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)close.2 8.2 (Berkeley) 4/19/94 35.\" 36.Dd April 19, 1994 37.Dt CLOSE 2 38.Os BSD 4 39.Sh NAME 40.Nm close 41.Nd delete a descriptor 42.Sh SYNOPSIS 43.Fd #include <unistd.h> 44.Ft int 45.Fo close 46.Fa "int fildes" 47.Fc 48.Sh DESCRIPTION 49The 50.Fn close 51call deletes a descriptor from the per-process object 52reference table. 53If this is the last reference to the underlying object, the 54object will be deactivated. 55For example, on the last close of a file 56the current 57.Em seek 58pointer associated with the file is lost; 59on the last close of a 60.Xr socket 2 61associated naming information and queued data are discarded; 62on the last close of a file holding an advisory lock 63the lock is released (see further 64.Xr flock 2 ) . 65.Pp 66When a process exits, 67all associated file descriptors are freed, but since there is 68a limit on active descriptors per processes, the 69.Fn close 70function call 71is useful when a large quantity of file descriptors are being handled. 72.Pp 73When a process forks (see 74.Xr fork 2 ) , 75all descriptors for the new child process reference the same 76objects as they did in the parent before the fork. 77If a new process is then to be run using 78.Xr execve 2 , 79the process would normally inherit these descriptors. Most 80of the descriptors can be rearranged with 81.Xr dup2 2 82or deleted with 83.Fn close 84before the 85.Xr execve 86is attempted, but if some of these descriptors will still 87be needed if the execve fails, it is necessary to arrange for them 88to be closed if the execve succeeds. 89For this reason, the call 90.Dq Li fcntl(d, F_SETFD, 1) 91is provided, 92which arranges that a descriptor will be closed after a successful 93execve; the call 94.Dq Li fcntl(d, F_SETFD, 0) 95restores the default, 96which is to not close the descriptor. 97.Sh RETURN VALUES 98Upon successful completion, a value of 0 is returned. 99Otherwise, a value of -1 is returned and the global integer variable 100.Va errno 101is set to indicate the error. 102.Sh ERRORS 103The 104.Fn close 105system call will fail if: 106.Bl -tag -width Er 107.\" ========== 108.It Bq Er EBADF 109.Fa fildes 110is not a valid, active file descriptor. 111.\" ========== 112.It Bq Er EINTR 113Its execution was interrupted by a signal. 114.\" ========== 115.It Bq Er EIO 116A previously-uncommitted 117.Xr write 2 118encountered an input/output error. 119.El 120.Sh SEE ALSO 121.Xr accept 2 , 122.Xr execve 2 , 123.Xr fcntl 2 , 124.Xr flock 2 , 125.Xr open 2 , 126.Xr pipe 2 , 127.Xr socket 2 , 128.Xr socketpair 2 129.Sh STANDARDS 130.Fn close 131conforms to 132.St -p1003.1-88 . 133