[apple/xnu.git] / bsd / man / man2 / close.2

.\"	$NetBSD: close.2,v 1.5 1995/02/27 12:32:14 cgd Exp $
.\"
.\" 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
.\"
.Dd April 19, 1994
.Dt CLOSE 2
.Os BSD 4
.Sh NAME
.Nm close
.Nd delete a descriptor
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fo close
.Fa "int fildes"
.Fc
.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 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
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
The
.Fn close
system call will fail if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EBADF
.Fa fildes
is not a valid, active file descriptor.
.\" ==========
.It Bq Er EINTR
Its execution was interrupted by a signal.
.\" ==========
.It Bq Er EIO
A previously-uncommitted
.Xr write 2
encountered an input/output error.
.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
.Fn Close
conforms to 
.St -p1003.1-88 .
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: close.2,v 1.5 1995/02/27 12:32:14 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993, 1994
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	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
2d21ac55 A	45	.Fo close
	46	.Fa "int fildes"
	47	.Fc
9bccf70c A	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
2d21ac55 A	103	The
	104	.Fn close
	105	system call will fail if:
9bccf70c	106	.Bl -tag -width Er
2d21ac55	107	.\" ==========
9bccf70c	108	.It Bq Er EBADF
2d21ac55 A	109	.Fa fildes
	110	is not a valid, active file descriptor.
	111	.\" ==========
9bccf70c	112	.It Bq Er EINTR
2d21ac55 A	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.
9bccf70c A	119	.El
	120	.Sh SEE ALSO
	121	.Xr accept 2 ,
2d21ac55 A	122	.Xr execve 2 ,
2d21ac55 A	123	.Xr fcntl 2 ,
9bccf70c A	124	.Xr flock 2 ,
	125	.Xr open 2 ,
	126	.Xr pipe 2 ,
	127	.Xr socket 2 ,
2d21ac55	128	.Xr socketpair 2
9bccf70c A	129	.Sh STANDARDS
	130	.Fn Close
	131	conforms to
	132	.St -p1003.1-88 .