[unix-history] / usr / src / lib / libc / sys / close.2

.\" Copyright (c) 1980, 1991 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	6.4 (Berkeley) 3/10/91
.\"
.Dd March 10, 1991
.Dt CLOSE 2
.Os BSD 4
.Sh NAME
.Nm close
.Nd delete a descriptor
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn close "int d"
.Sh DESCRIPTION
The
.Fn close
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 ) .
.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
function call
is useful when a large quanitity 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
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, 1)
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
Upon successful completion, a value of 0 is returned.
Otherwise, a value of -1 is returned and the global integer variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Close
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa D
is not an active descriptor.
.It Bq Er EINTR
An interupt was received.
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr flock 2 ,
.Xr open 2 ,
.Xr pipe 2 ,
.Xr socket 2 ,
.Xr socketpair 2 ,
.Xr execve 2 ,
.Xr fcntl 2
.Sh STANDARDS
.Fn Close
conforms to IEEE Std 1003.1-1988
.Pq Dq Tn POSIX .
Commit	Line	Data
e05f49cf WJ	1	.\" Copyright (c) 1980, 1991 Regents of the University of California.
	2	.\" 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. All advertising materials mentioning features or use of this software
	13	.\" must display the following acknowledgement:
	14	.\" This product includes software developed by the University of
	15	.\" California, Berkeley and its contributors.
	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)close.2 6.4 (Berkeley) 3/10/91
	33	.\"
	34	.Dd March 10, 1991
	35	.Dt CLOSE 2
	36	.Os BSD 4
	37	.Sh NAME
	38	.Nm close
	39	.Nd delete a descriptor
	40	.Sh SYNOPSIS
	41	.Fd #include <unistd.h>
	42	.Ft int
	43	.Fn close "int d"
	44	.Sh DESCRIPTION
	45	The
	46	.Fn close
	47	call deletes a descriptor from the per-process object
	48	reference table.
	49	If this is the last reference to the underlying object, the
	50	object will be deactivated.
	51	For example, on the last close of a file
	52	the current
	53	.Em seek
	54	pointer associated with the file is lost;
	55	on the last close of a
	56	.Xr socket 2
	57	associated naming information and queued data are discarded;
	58	on the last close of a file holding an advisory lock
	59	the lock is released (see further
	60	.Xr flock 2 ) .
	61	.Pp
	62	When a process exits,
	63	all associated file descriptors are freed, but since there is
	64	a limit on active descriptors per processes, the
65	.Fn close
66	function call
67	is useful when a large quanitity of file descriptors are being handled.
68	.Pp
69	When a process forks (see
70	.Xr fork 2 ) ,
71	all descriptors for the new child process reference the same
72	objects as they did in the parent before the fork.
73	If a new process is then to be run using
74	.Xr execve 2 ,
75	the process would normally inherit these descriptors. Most
76	of the descriptors can be rearranged with
77	.Xr dup2 2
78	or deleted with
79	.Fn close
80	before the
81	.Xr execve
82	is attempted, but if some of these descriptors will still
83	be needed if the execve fails, it is necessary to arrange for them
84	to be closed if the execve succeeds.
85	For this reason, the call
86	.Dq Li fcntl(d, F_SETFD, 1)
87	is provided,
88	which arranges that a descriptor will be closed after a successful
89	execve; the call
90	.Dq Li fcntl(d, F_SETFD, 0)
91	restores the default,
92	which is to not close the descriptor.
93	.Sh RETURN VALUES
94	Upon successful completion, a value of 0 is returned.
95	Otherwise, a value of -1 is returned and the global integer variable
96	.Va errno
97	is set to indicate the error.
98	.Sh ERRORS
99	.Fn Close
100	will fail if:
101	.Bl -tag -width Er
102	.It Bq Er EBADF
103	.Fa D
104	is not an active descriptor.
105	.It Bq Er EINTR
106	An interupt was received.
107	.El
108	.Sh SEE ALSO
109	.Xr accept 2 ,
110	.Xr flock 2 ,
111	.Xr open 2 ,
112	.Xr pipe 2 ,
113	.Xr socket 2 ,
114	.Xr socketpair 2 ,
115	.Xr execve 2 ,
116	.Xr fcntl 2
117	.Sh STANDARDS
118	.Fn Close
119	conforms to IEEE Std 1003.1-1988
120	.Pq Dq Tn POSIX .