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1 .\" $NetBSD: close.2,v 1.5 1995/02/27 12:32:14 cgd Exp $
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34 .\" @(#)close.2 8.2 (Berkeley) 4/19/94
35 .\"
36 .Dd April 19, 1994
37 .Dt CLOSE 2
38 .Os BSD 4
39 .Sh NAME
40 .Nm close
41 .Nd delete a descriptor
42 .Sh SYNOPSIS
43 .Fd #include <unistd.h>
44 .Ft int
45 .Fo close
46 .Fa "int fildes"
47 .Fc
48 .Sh DESCRIPTION
49 The
50 .Fn close
51 call deletes a descriptor from the per-process object
52 reference table.
53 If this is the last reference to the underlying object, the
54 object will be deactivated.
55 For example, on the last close of a file
56 the current
57 .Em seek
58 pointer associated with the file is lost;
59 on the last close of a
60 .Xr socket 2
61 associated naming information and queued data are discarded;
62 on the last close of a file holding an advisory lock
63 the lock is released (see further
64 .Xr flock 2 ) .
65 .Pp
66 When a process exits,
67 all associated file descriptors are freed, but since there is
68 a limit on active descriptors per processes, the
69 .Fn close
70 function call
71 is useful when a large quantity of file descriptors are being handled.
72 .Pp
73 When a process forks (see
74 .Xr fork 2 ) ,
75 all descriptors for the new child process reference the same
76 objects as they did in the parent before the fork.
77 If a new process is then to be run using
78 .Xr execve 2 ,
79 the process would normally inherit these descriptors. Most
80 of the descriptors can be rearranged with
81 .Xr dup2 2
82 or deleted with
83 .Fn close
84 before the
85 .Xr execve
86 is attempted, but if some of these descriptors will still
87 be needed if the execve fails, it is necessary to arrange for them
88 to be closed if the execve succeeds.
89 For this reason, the call
90 .Dq Li fcntl(d, F_SETFD, 1)
91 is provided,
92 which arranges that a descriptor will be closed after a successful
93 execve; the call
94 .Dq Li fcntl(d, F_SETFD, 0)
95 restores the default,
96 which is to not close the descriptor.
97 .Sh RETURN VALUES
98 Upon successful completion, a value of 0 is returned.
99 Otherwise, a value of -1 is returned and the global integer variable
100 .Va errno
101 is set to indicate the error.
102 .Sh ERRORS
103 The
104 .Fn close
105 system call will fail if:
106 .Bl -tag -width Er
107 .\" ==========
108 .It Bq Er EBADF
109 .Fa fildes
110 is not a valid, active file descriptor.
111 .\" ==========
112 .It Bq Er EINTR
113 Its execution was interrupted by a signal.
114 .\" ==========
115 .It Bq Er EIO
116 A previously-uncommitted
117 .Xr write 2
118 encountered an input/output error.
119 .El
120 .Sh SEE ALSO
121 .Xr accept 2 ,
122 .Xr execve 2 ,
123 .Xr fcntl 2 ,
124 .Xr flock 2 ,
125 .Xr open 2 ,
126 .Xr pipe 2 ,
127 .Xr socket 2 ,
128 .Xr socketpair 2
129 .Sh STANDARDS
130 .Fn Close
131 conforms to
132 .St -p1003.1-88 .