close.2 (66492cf01c4f0eb178cb6e056451d04be61a0374) | close.2 (1fa2a66491e7d8ae0be84e7da4da8e812480c710) |
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1.\" 2.\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for 3.\" permission to reproduce portions of its copyrighted documentation. 4.\" Original documentation from The Open Group can be obtained online at 5.\" http://www.opengroup.org/bookstore/. 6.\" 7.\" The Institute of Electrical and Electronics Engineers and The Open 8.\" Group, have given us permission to reprint portions of their --- 29 unchanged lines hidden (view full) --- 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. | 1.\" 2.\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for 3.\" permission to reproduce portions of its copyrighted documentation. 4.\" Original documentation from The Open Group can be obtained online at 5.\" http://www.opengroup.org/bookstore/. 6.\" 7.\" The Institute of Electrical and Electronics Engineers and The Open 8.\" Group, have given us permission to reprint portions of their --- 29 unchanged lines hidden (view full) --- 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 |
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46.\" | 47.\" |
47.TH CLOSE 2 "Oct 18, 2005" 48.SH NAME 49close \- close a file descriptor 50.SH SYNOPSIS 51.LP 52.nf 53#include <unistd.h> 54 55\fBint\fR \fBclose\fR(\fBint\fR \fIfildes\fR); 56.fi 57 58.SH DESCRIPTION 59.sp 60.LP 61The \fBclose()\fR function deallocates the file descriptor indicated by 62\fIfildes\fR. To deallocate means to make the file descriptor available for 63return by subsequent calls to \fBopen\fR(2) or other functions that allocate 64file descriptors. All outstanding record locks owned by the process on the file 65associated with the file descriptor will be removed (that is, unlocked). 66.sp 67.LP 68If \fBclose()\fR is interrupted by a signal that is to be caught, it will 69return \fB\(mi1\fR with \fBerrno\fR set to \fBEINTR\fR and the state of 70\fIfildes\fR is unspecified. If an I/O error occurred while reading from or 71writing to the file system during \fBclose()\fR, it returns -1, sets 72\fBerrno\fR to \fBEIO\fR, and the state of \fIfildes\fR is unspecified. 73.sp 74.LP 75When all file descriptors associated with a pipe or \fBFIFO\fR special file are 76closed, any data remaining in the pipe or \fBFIFO\fR will be discarded. 77.sp 78.LP | 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 |
79When all file descriptors associated with an open file description have been 80closed the open file description will be freed. | 99When all file descriptors associated with an open file description have been 100closed the open file description will be freed. |
81.sp 82.LP 83If the link count of the file is 0, when all file descriptors associated with 84the file are closed, the space occupied by the file will be freed and the file 85will no longer be accessible. 86.sp 87.LP 88If a streams-based (see \fBIntro\fR(2)) \fIfildes\fR is closed and the calling 89process was previously registered to receive a \fBSIGPOLL\fR signal (see 90\fBsignal\fR(3C)) for events associated with that stream (see \fBI_SETSIG\fR in 91\fBstreamio\fR(7I)), the calling process will be unregistered for events 92associated with the stream. The last \fBclose()\fR for a stream causes the 93stream associated with \fIfildes\fR to be dismantled. If \fBO_NONBLOCK\fR and 94\fBO_NDELAY\fR are not set and there have been no signals posted for the 95stream, and if there is data on the module's write queue, \fBclose()\fR waits 96up to 15 seconds (for each module and driver) for any output to drain before 97dismantling the stream. The time delay can be changed via an \fBI_SETCLTIME\fR 98\fBioctl\fR(2) request (see \fBstreamio\fR(7I)). If the \fBO_NONBLOCK\fR or 99\fBO_NDELAY\fR flag is set, or if there are any pending signals, \fBclose()\fR | 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 7I 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 7I 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 |
100does not wait for output to drain, and dismantles the stream immediately. | 158does not wait for output to drain, and dismantles the stream immediately. |
101.sp 102.LP 103If \fIfildes\fR is associated with one end of a pipe, the last \fBclose()\fR 104causes a hangup to occur on the other end of the pipe. In addition, if the 105other end of the pipe has been named by \fBfattach\fR(3C), then the last 106\fBclose()\fR forces the named end to be detached by \fBfdetach\fR(3C). If the 107named end has no open file descriptors associated with it and gets detached, 108the stream associated with that end is also dismantled. 109.sp 110.LP 111If \fIfildes\fR refers to the master side of a pseudo-terminal, a \fBSIGHUP\fR 112signal is sent to the session leader, if any, for which the slave side of the 113pseudo-terminal is the controlling terminal. It is unspecified whether closing 114the master side of the pseudo-terminal flushes all queued input and output. 115.sp 116.LP 117If \fIfildes\fR refers to the slave side of a streams-based pseudo-terminal, a 118zero-length message may be sent to the master. 119.sp 120.LP | 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 |
121When there is an outstanding cancelable asynchronous I/O operation against | 188When there is an outstanding cancelable asynchronous I/O operation against |
122\fIfildes\fR when \fBclose()\fR is called, that I/O operation is canceled. An 123I/O operation that is not canceled completes as if the \fBclose()\fR operation 124had not yet occurred. All operations that are not canceled will complete as if 125the \fBclose()\fR blocked until the operations completed. 126.sp 127.LP | 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 |
128If a shared memory object or a memory mapped file remains referenced at the | 200If a shared memory object or a memory mapped file remains referenced at the |
129last close (that is, a process has it mapped), then the entire contents of the 130memory object will persist until the memory object becomes unreferenced. If 131this is the last close of a shared memory object or a memory mapped file and | 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 |
132the close results in the memory object becoming unreferenced, and the memory 133object has been unlinked, then the memory object will be removed. | 206the close results in the memory object becoming unreferenced, and the memory 207object has been unlinked, then the memory object will be removed. |
134.sp 135.LP 136If \fIfildes\fR refers to a socket, \fBclose()\fR causes the socket to be 137destroyed. If the socket is connection-mode, and the \fBSO_LINGER\fR option is 138set for the socket with non-zero linger time, and the socket has untransmitted 139data, then \fBclose()\fR will block for up to the current linger interval until 140all data is transmitted. 141.SH RETURN VALUES 142.sp 143.LP 144Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is 145returned and \fBerrno\fR is set to indicate the error. 146.SH ERRORS 147.sp 148.LP 149The \fBclose()\fR function will fail if: 150.sp 151.ne 2 152.na 153\fB\fBEBADF\fR\fR 154.ad 155.RS 11n 156The \fIfildes\fR argument is not a valid file descriptor. 157.RE 158 159.sp 160.ne 2 161.na 162\fB\fBEINTR\fR\fR 163.ad 164.RS 11n 165The \fBclose()\fR function was interrupted by a signal. 166.RE 167 168.sp 169.ne 2 170.na 171\fB\fBENOLINK\fR\fR 172.ad 173.RS 11n 174The \fIfildes\fR argument is on a remote machine and the link to that machine 175is no longer active. 176.RE 177 178.sp 179.ne 2 180.na 181\fB\fBENOSPC\fR\fR 182.ad 183.RS 11n 184There was no free space remaining on the device containing the file. 185.RE 186 187.sp 188.LP 189The \fBclose()\fR function may fail if: 190.sp 191.ne 2 192.na 193\fB\fBEIO\fR\fR 194.ad 195.RS 7n 196An I/O error occurred while reading from or writing to the file system. 197.RE 198 199.SH EXAMPLES 200.LP 201\fBExample 1 \fRReassign a file descriptor. 202.sp 203.LP | 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 |
204The following example closes the file descriptor associated with standard 205output for the current process, re-assigns standard output to a new file | 226The following example closes the file descriptor associated with standard 227output for the current process, re-assigns standard output to a new file |
206descriptor, and closes the original file descriptor to clean up. This example 207assumes that the file descriptor 0, which is the descriptor for standard input, 208is not closed. 209 210.sp 211.in +2 212.nf | 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 |
213#include <unistd.h> 214\&... 215int pfd; 216\&... 217close(1); 218dup(pfd); 219close(pfd); 220\&... | 233#include <unistd.h> 234\&... 235int pfd; 236\&... 237close(1); 238dup(pfd); 239close(pfd); 240\&... |
221.fi 222.in -2 223 224.sp 225.LP | 241.Ed 242.Pp |
226Incidentally, this is exactly what could be achieved using: | 243Incidentally, this is exactly what could be achieved using: |
227 228.sp 229.in +2 230.nf | 244.Bd -literal -offset Ds |
231dup2(pfd, 1); 232close(pfd); | 245dup2(pfd, 1); 246close(pfd); |
233.fi 234.in -2 235 236.LP 237\fBExample 2 \fRClose a file descriptor. 238.sp 239.LP 240In the following example, \fBclose()\fR is used to close a file descriptor 241after an unsuccessful attempt is made to associate that file descriptor with a 242stream. 243 244.sp 245.in +2 246.nf | 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 |
247#include <stdio.h> 248#include <unistd.h> 249#include <stdlib.h> 250 251#define LOCKFILE "/etc/ptmp" 252\&... 253int pfd; 254FILE *fpfd; 255\&... 256if ((fpfd = fdopen (pfd, "w")) == NULL) { 257 close(pfd); 258 unlink(LOCKFILE); 259 exit(1); 260} 261\&... | 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\&... |
262.fi 263.in -2 264 265.SH USAGE 266.sp 267.LP 268An application that used the \fBstdio\fR function \fBfopen\fR(3C) to open a 269file should use the corresponding \fBfclose\fR(3C) function rather than 270\fBclose()\fR. 271.SH ATTRIBUTES 272.sp 273.LP 274See \fBattributes\fR(5) for descriptions of the following attributes: 275.sp 276 277.sp 278.TS 279box; 280c | c 281l | l . 282ATTRIBUTE TYPE ATTRIBUTE VALUE 283_ 284Interface Stability Standard 285_ 286MT-Level Async-Signal-Safe 287.TE 288 289.SH SEE ALSO 290.sp 291.LP 292\fBIntro\fR(2), \fBcreat\fR(2), \fBdup\fR(2), \fBexec\fR(2), \fBfcntl\fR(2), 293\fBioctl\fR(2), \fBopen\fR(2) \fBpipe\fR(2), \fBfattach\fR(3C), 294\fBfclose\fR(3C), \fBfdetach\fR(3C), \fBfopen\fR(3C), \fBsignal\fR(3C), 295\fBsignal.h\fR(3HEAD), \fBattributes\fR(5), \fBstandards\fR(5), 296\fBstreamio\fR(7I) | 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 attributes 5 , 331.Xr standards 5 , 332.Xr streamio 7I |