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.\" @(#)close.2 8.2 (Berkeley) 4/19/94 29.\" $FreeBSD$ 30.\" 31.Dd December 1, 2017 32.Dt CLOSE 2 33.Os 34.Sh NAME 35.Nm close 36.Nd delete a descriptor 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft int 42.Fn close "int fd" 43.Sh DESCRIPTION 44The 45.Fn close 46system call deletes a descriptor from the per-process object 47reference table. 48If this is the last reference to the underlying object, the 49object will be deactivated. 50For example, on the last close of a file 51the current 52.Em seek 53pointer associated with the file is lost; 54on the last close of a 55.Xr socket 2 56associated naming information and queued data are discarded; 57on the last close of a file holding an advisory lock 58the lock is released (see further 59.Xr flock 2 ) . 60However, the semantics of System V and 61.St -p1003.1-88 62dictate that all 63.Xr fcntl 2 64advisory record locks associated with a file for a given process 65are removed when 66.Em any 67file descriptor for that file is closed by that process. 68.Pp 69When a process exits, 70all associated file descriptors are freed, but since there is 71a limit on active descriptors per processes, the 72.Fn close 73system call 74is useful when a large quantity of file descriptors are being handled. 75.Pp 76When a process forks (see 77.Xr fork 2 ) , 78all descriptors for the new child process reference the same 79objects as they did in the parent before the fork. 80If a new process is then to be run using 81.Xr execve 2 , 82the process would normally inherit these descriptors. 83Most 84of the descriptors can be rearranged with 85.Xr dup2 2 86or deleted with 87.Fn close 88before the 89.Xr execve 2 90is attempted, but if some of these descriptors will still 91be needed if the execve fails, it is necessary to arrange for them 92to be closed if the execve succeeds. 93For this reason, the call 94.Dq Li fcntl(d, F_SETFD, FD_CLOEXEC) 95is provided, 96which arranges that a descriptor will be closed after a successful 97execve; the call 98.Dq Li fcntl(d, F_SETFD, 0) 99restores the default, 100which is to not close the descriptor. 101.Sh RETURN VALUES 102.Rv -std close 103.Sh ERRORS 104The 105.Fn close 106system call will fail if: 107.Bl -tag -width Er 108.It Bq Er EBADF 109The 110.Fa fd 111argument 112is not an active descriptor. 113.It Bq Er EINTR 114An interrupt was received. 115.It Bq Er ENOSPC 116The underlying object did not fit, cached data was lost. 117.It Bq Er ECONNRESET 118The underlying object was a stream socket that was shut down by the peer 119before all pending data was delivered. 120.El 121.Pp 122In case of any error except 123.Er EBADF , 124the supplied file descriptor is deallocated and therefore is no longer valid. 125.Sh SEE ALSO 126.Xr accept 2 , 127.Xr closefrom 2 , 128.Xr execve 2 , 129.Xr fcntl 2 , 130.Xr flock 2 , 131.Xr open 2 , 132.Xr pipe 2 , 133.Xr socket 2 , 134.Xr socketpair 2 135.Sh STANDARDS 136The 137.Fn close 138system call is expected to conform to 139.St -p1003.1-90 . 140.Sh HISTORY 141The 142.Fn close 143function appeared in 144.At v1 . 145