1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
.\" Copyright (c) 1980, 1991, 1993, 1994
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)close.2 8.2 (Berkeley) 4/19/94
.\" $FreeBSD$
.\"
.Dd April 19, 1994
.Dt CLOSE 2
.Os
.Sh NAME
.Nm close
.Nd delete a descriptor
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn close "int d"
.Sh DESCRIPTION
The
.Fn close
system call deletes a descriptor from the per-process object
reference table.
If this is the last reference to the underlying object, the
object will be deactivated.
For example, on the last close of a file
the current
.Em seek
pointer associated with the file is lost;
on the last close of a
.Xr socket 2
associated naming information and queued data are discarded;
on the last close of a file holding an advisory lock
the lock is released (see further
.Xr flock 2 ) .
However, the semantics of System V and
.St -p1003.1-88
dictate that all
.Xr fcntl 2
advisory record locks associated with a file for a given process
are removed when
.Em any
file descriptor for that file is closed by that process.
.Pp
When a process exits,
all associated file descriptors are freed, but since there is
a limit on active descriptors per processes, the
.Fn close
system call
is useful when a large quantity of file descriptors are being handled.
.Pp
When a process forks (see
.Xr fork 2 ) ,
all descriptors for the new child process reference the same
objects as they did in the parent before the fork.
If a new process is then to be run using
.Xr execve 2 ,
the process would normally inherit these descriptors. Most
of the descriptors can be rearranged with
.Xr dup2 2
or deleted with
.Fn close
before the
.Xr execve 2
is attempted, but if some of these descriptors will still
be needed if the execve fails, it is necessary to arrange for them
to be closed if the execve succeeds.
For this reason, the call
.Dq Li fcntl(d, F_SETFD, FD_CLOEXEC)
is provided,
which arranges that a descriptor will be closed after a successful
execve; the call
.Dq Li fcntl(d, F_SETFD, 0)
restores the default,
which is to not close the descriptor.
.Sh RETURN VALUES
.Rv -std close
.Sh ERRORS
The
.Fn close
system call will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa d
argument
is not an active descriptor.
.It Bq Er EINTR
An interrupt was received.
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr execve 2 ,
.Xr fcntl 2 ,
.Xr flock 2 ,
.Xr open 2 ,
.Xr pipe 2 ,
.Xr socket 2 ,
.Xr socketpair 2
.Sh STANDARDS
The
.Fn close
system call is expected to conform to
.St -p1003.1-90 .
.Sh HISTORY
The
.Fn close
function appeared in
.At v7 .
|