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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd December 1, 2017 29.Dt CLOSE 2 30.Os 31.Sh NAME 32.Nm close 33.Nd delete a descriptor 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In unistd.h 38.Ft int 39.Fn close "int fd" 40.Sh DESCRIPTION 41The 42.Fn close 43system call deletes a descriptor from the per-process object 44reference table. 45If this is the last reference to the underlying object, the 46object will be deactivated. 47For example, on the last close of a file 48the current 49.Em seek 50pointer associated with the file is lost; 51on the last close of a 52.Xr socket 2 53associated naming information and queued data are discarded; 54on the last close of a file holding an advisory lock 55the lock is released (see further 56.Xr flock 2 ) . 57However, the semantics of System V and 58.St -p1003.1-88 59dictate that all 60.Xr fcntl 2 61advisory record locks associated with a file for a given process 62are removed when 63.Em any 64file descriptor for that file is closed by that process. 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 70system 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. 80Most 81of the descriptors can be rearranged with 82.Xr dup2 2 83or deleted with 84.Fn close 85before the 86.Xr execve 2 87is attempted, but if some of these descriptors will still 88be needed if the execve fails, it is necessary to arrange for them 89to be closed if the execve succeeds. 90For this reason, the call 91.Dq Li fcntl(d, F_SETFD, FD_CLOEXEC) 92is provided, 93which arranges that a descriptor will be closed after a successful 94execve; the call 95.Dq Li fcntl(d, F_SETFD, 0) 96restores the default, 97which is to not close the descriptor. 98.Sh RETURN VALUES 99.Rv -std close 100.Sh ERRORS 101The 102.Fn close 103system call will fail if: 104.Bl -tag -width Er 105.It Bq Er EBADF 106The 107.Fa fd 108argument 109is not an active descriptor. 110.It Bq Er EINTR 111An interrupt was received. 112.It Bq Er ENOSPC 113The underlying object did not fit, cached data was lost. 114.It Bq Er ECONNRESET 115The underlying object was a stream socket that was shut down by the peer 116before all pending data was delivered. 117.El 118.Pp 119In case of any error except 120.Er EBADF , 121the supplied file descriptor is deallocated and therefore is no longer valid. 122.Sh SEE ALSO 123.Xr accept 2 , 124.Xr closefrom 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 135system call is expected to conform to 136.St -p1003.1-90 . 137.Sh HISTORY 138The 139.Fn close 140function appeared in 141.At v1 . 142