1.\" $NetBSD: close.2,v 1.12 2002/02/08 01:28:17 ross 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 39.Sh NAME 40.Nm close 41.Nd delete a descriptor 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]unistd.h\*[Gt] 46.Ft int 47.Fn close "int d" 48.Sh DESCRIPTION 49The 50.Fn close 51system call 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 the current 56.Em seek 57pointer associated with the file is lost; on the last close of a 58.Xr socket 2 59associated naming information and queued data are discarded; on 60the last close of a file holding an advisory lock the lock is 61released (see 62.Xr flock 2 ) . 63.Pp 64When a process exits, all associated descriptors are freed, but 65since there is a limit on active descriptors per processes, the 66.Fn close 67system call 68is useful when a large quantity of file descriptors are being handled. 69.Pp 70When a process calls 71.Xr fork 2 , 72all descriptors for the new child process reference the same 73objects as they did in the parent before the 74.Fn fork . 75If a new process is then to be run using 76.Xr execve 2 , 77the process would normally inherit these descriptors. 78Most of the descriptors can be rearranged with 79.Xr dup2 2 80or deleted with 81.Fn close 82before the 83.Fn execve 84is attempted, but if some of these descriptors will still be needed if the 85.Fn execve 86fails, it is necessary to arrange for them to be closed only if the 87.Fn execve 88succeeds. 89For this reason, the system call 90.Bl -item -offset indent 91.It 92.Fn fcntl d F_SETFD 1 ; 93.El 94.Pp 95is provided, 96which arranges that a descriptor 97.Dq Fa d 98will be closed after a successful 99.Fn execve ; 100the system call 101.Bl -item -offset indent 102.It 103.Fn fcntl d F_SETFD 0 ; 104.El 105.Pp 106restores the default, which is to not close descriptor 107.Dq Fa d . 108.Sh RETURN VALUES 109Upon successful completion, a value of 0 is returned. 110Otherwise, a value of -1 is returned and the global integer variable 111.Va errno 112is set to indicate the error. 113.Sh ERRORS 114.Fn close 115will fail if: 116.Bl -tag -width Er 117.It Bq Er EBADF 118.Fa d 119is not an active descriptor. 120.It Bq Er EINTR 121An interrupt was received. 122.El 123.Sh SEE ALSO 124.Xr accept 2 , 125.Xr execve 2 , 126.Xr fcntl 2 , 127.Xr flock 2 , 128.Xr open 2 , 129.Xr pipe 2 , 130.Xr socket 2 , 131.Xr socketpair 2 132.Sh STANDARDS 133The 134.Fn close 135function conforms to 136.St -p1003.1-90 . 137