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In the event of any discrepancy 20.\" between these versions and the original IEEE and The Open Group 21.\" Standard, the original IEEE and The Open Group Standard is the referee 22.\" document. The original Standard can be obtained online at 23.\" http://www.opengroup.org/unix/online.html. 24.\" 25.\" This notice shall appear on any product containing this material. 26.\" 27.\" The contents of this file are subject to the terms of the 28.\" Common Development and Distribution License (the "License"). 29.\" You may not use this file except in compliance with the License. 30.\" 31.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 32.\" or http://www.opensolaris.org/os/licensing. 33.\" See the License for the specific language governing permissions 34.\" and limitations under the License. 35.\" 36.\" When distributing Covered Code, include this CDDL HEADER in each 37.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE. 38.\" If applicable, add the following below this CDDL HEADER, with the 39.\" fields enclosed by brackets "[]" replaced with your own identifying 40.\" information: Portions Copyright [yyyy] [name of copyright owner] 41.\" 42.\" 43.\" Copyright 1989 AT&T 44.\" Portions Copyright (c) 1992, X/Open Company Limited. All Rights Reserved. 45.\" Copyright (c) 2005, Sun Microsystems, Inc. All Rights Reserved. 46.\" Copyright 2022 Oxide Computer Company 47.\" 48.Dd February 5, 2022 49.Dt CLOSE 2 50.Os 51.Sh NAME 52.Nm close 53.Nd close a file descriptor 54.Sh SYNOPSIS 55.In unistd.h 56.Ft int 57.Fo close 58.Fa "int fildes" 59.Fc 60.Sh DESCRIPTION 61The 62.Fn close 63function deallocates the file descriptor indicated by 64.Fa fildes . 65To deallocate means to make the file descriptor available for return by 66subsequent calls to 67.Xr open 2 68or other functions that allocate file descriptors. 69All outstanding record locks owned by the process on the file associated with 70the file descriptor will be removed 71.Pq "that is, unlocked" . 72.Pp 73If 74.Fn close 75is interrupted by a signal that is to be caught, it will return 76.Sy -1 77with 78.Va errno 79set to 80.Er EINTR 81and the state of 82.Fa fildes 83is unspecified. 84If an I/O error occurred while reading from or writing to the file system during 85.Fn close , 86it returns 87.Sy -1 , 88sets 89.Va errno 90to 91.Er EIO , 92and the state of 93.Fa fildes 94is unspecified. 95.Pp 96When all file descriptors associated with a pipe or FIFO special file are 97closed, any data remaining in the pipe or FIFO will be discarded. 98.Pp 99When all file descriptors associated with an open file description have been 100closed the open file description will be freed. 101.Pp 102If the link count of the file is 103.Sy 0 , 104when all file descriptors associated with the file are closed, the space 105occupied by the file will be freed and the file will no longer be accessible. 106.Pp 107If a streams-based 108.Po 109see 110.Xr Intro 2 111.Pc 112.Fa fildes 113is closed and the calling process was previously registered to receive a 114.Dv SIGPOLL 115signal 116.Po 117see 118.Xr signal 3C 119.Pc 120for events associated with that stream 121.Po 122see 123.Dv I_SETSIG 124in 125.Xr streamio 4I 126.Pc , 127the calling process will be unregistered for events associated with the stream. 128The last 129.Fn close 130for a stream causes the stream associated with 131.Fa fildes 132to be dismantled. 133If 134.Dv O_NONBLOCK 135and 136.Dv O_NDELAY 137are not set and there have been no signals posted for the stream, and if there 138is data on the module's write queue, 139.Fn close 140waits up to 15 seconds 141.Pq for each module and driver 142for any output to drain 143before dismantling the stream. 144The time delay can be changed via an 145.Dv I_SETCLTIME 146.Xr ioctl 2 147request 148.Po 149see 150.Xr streamio 4I 151.Pc . 152If the 153.Dv O_NONBLOCK 154or 155.Dv O_NDELAY 156flag is set, or if there are any pending signals, 157.Fn close 158does not wait for output to drain, and dismantles the stream immediately. 159.Pp 160If 161.Fa fildes 162is associated with one end of a pipe, the last 163.Fn close 164causes a hangup to occur on the other end of the pipe. 165In addition, if the other end of the pipe has been named by 166.Xr fattach 3C , 167then the last 168.Fn close 169forces the named end to be detached by 170.Xr fdetach 3C . 171If the named end has no open file descriptors associated with it and gets 172detached, the stream associated with that end is also dismantled. 173.Pp 174If 175.Fa fildes 176refers to the manager side of a pseudo-terminal, a 177.Dv SIGHUP 178signal is sent to the session leader, if any, for which the subsidiary side of 179the pseudo-terminal is the controlling terminal. 180It is unspecified whether closing the manager side of the pseudo-terminal 181flushes all queued input and output. 182.Pp 183If 184.Fa fildes 185refers to the subsidiary side of a streams-based pseudo-terminal, a zero-length 186message may be sent to the manager. 187.Pp 188When there is an outstanding cancelable asynchronous I/O operation against 189.Fa fildes 190when 191.Fn close 192is called, that I/O operation is canceled. 193An I/O operation that is not canceled completes as if the 194.Fn close 195operation had not yet occurred. 196All operations that are not canceled will complete as if the 197.Fn close 198blocked until the operations completed. 199.Pp 200If a shared memory object or a memory mapped file remains referenced at the 201last close 202.Pq "that is, a process has it mapped" , 203then the entire contents of the memory object will persist until the memory 204object becomes unreferenced. 205If this is the last close of a shared memory object or a memory mapped file and 206the close results in the memory object becoming unreferenced, and the memory 207object has been unlinked, then the memory object will be removed. 208.Pp 209If 210.Fa fildes 211refers to a socket, 212.Fn close 213causes the socket to be destroyed. 214If the socket is connection-mode, and the 215.Dv SO_LINGER 216option is set for the socket with non-zero linger time, and the socket has 217untransmitted data, then 218.Fn close 219will block for up to the current linger interval until all data is transmitted. 220.Sh RETURN VALUES 221.Rv -std close 222.Sh EXAMPLES 223.Sy Example 1 224Reassign a file descriptor. 225.Pp 226The following example closes the file descriptor associated with standard 227output for the current process, re-assigns standard output to a new file 228descriptor, and closes the original file descriptor to clean up. 229This example assumes that the file descriptor 230.Sy 0 , 231which is the descriptor for standard input, is not closed. 232.Bd -literal -offset Ds 233#include <unistd.h> 234\&... 235int pfd; 236\&... 237close(1); 238dup(pfd); 239close(pfd); 240\&... 241.Ed 242.Pp 243Incidentally, this is exactly what could be achieved using: 244.Bd -literal -offset Ds 245dup2(pfd, 1); 246close(pfd); 247.Ed 248.Pp 249.Sy Example 2 250Close a file descriptor. 251.Pp 252In the following example, 253.Fn close 254is used to close a file descriptor after an unsuccessful attempt is made to 255associate that file descriptor with a stream. 256.Bd -literal -offset Ds 257#include <stdio.h> 258#include <unistd.h> 259#include <stdlib.h> 260 261#define LOCKFILE "/etc/ptmp" 262\&... 263int pfd; 264FILE *fpfd; 265\&... 266if ((fpfd = fdopen (pfd, "w")) == NULL) { 267 close(pfd); 268 unlink(LOCKFILE); 269 exit(1); 270} 271\&... 272.Ed 273.Sh ERRORS 274The 275.Fn close 276function will fail if: 277.Bl -tag -width Er 278.It Er EBADF 279The 280.Fa fildes 281argument is not a valid file descriptor. 282.It Er EINTR 283The 284.Fn close 285function was interrupted by a signal. 286.It Er ENOLINK 287The 288.Fa fildes 289argument is on a remote machine and the link to that machine is no longer 290active. 291.It Er ENOSPC 292There was no free space remaining on the device containing the file. 293.El 294.Pp 295The 296.Fn close 297function may fail if: 298.Bl -tag -width Er 299.It Er EIO 300An I/O error occurred while reading from or writing to the file system. 301.El 302.Sh USAGE 303An application that used the 304.Xr stdio 3C 305function 306.Xr fopen 3C 307to open a file should use the corresponding 308.Xr fclose 3C 309function rather than 310.Fn close . 311.Sh INTERFACE STABILITY 312.Sy Committed 313.Sh MT-LEVEL 314.Sy Async-Signal-Safe 315.Sh SEE ALSO 316.Xr creat 2 , 317.Xr dup 2 , 318.Xr exec 2 , 319.Xr fcntl 2 , 320.Xr Intro 2 , 321.Xr ioctl 2 , 322.Xr open 2 , 323.Xr pipe 2 , 324.Xr fattach 3C , 325.Xr fclose 3C , 326.Xr fdetach 3C , 327.Xr fopen 3C , 328.Xr signal 3C , 329.Xr signal.h 3HEAD , 330.Xr streamio 4I , 331.Xr attributes 7 , 332.Xr standards 7 333