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

.\"	$NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $
.\"
.\" Copyright (c) 1993
.\"	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.
.\"
.\"	@(#)pathconf.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt PATHCONF 2
.Os BSD 4
.Sh NAME
.Nm fpathconf ,
.Nm pathconf
.Nd get configurable pathname variables
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft long
.Fo fpathconf
.Fa "int fildes"
.Fa "int name"
.Fc
.Ft long
.Fo pathconf
.Fa "const char *path"
.Fa "int name"
.Fc
.Sh DESCRIPTION
.Pp
The
.Fn pathconf
and
.Fn fpathconf
functions provides a method for applications to determine the current
value of a configurable system limit or option variable associated
with a pathname or file descriptor.
.Pp
For
.Nm pathconf ,
the
.Fa path
argument is the name of a file or directory.
For
.Nm fpathconf ,
the
.Fa fildes
argument is an open file descriptor.
The
.Fa name
argument specifies the system variable to be queried.
Symbolic constants for each name value are found in the include file
.Li <unistd.h> .
.Pp
The available values are as follows:
.Pp
.Bl -tag -width "123456"
.Pp
.It Li _PC_LINK_MAX
The maximum file link count.
.It Li _PC_MAX_CANON
The maximum number of bytes in terminal canonical input line.
.It Li _PC_MAX_INPUT
The minimum maximum number of bytes for which space is available in
a terminal input queue.
.It Li _PC_NAME_MAX
The maximum number of bytes in a file name.
.It Li _PC_PATH_MAX
The maximum number of bytes in a pathname.
.It Li _PC_PIPE_BUF
The maximum number of bytes which will be written atomically to a pipe.
.It Li _PC_CHOWN_RESTRICTED
Return 1 if appropriate privileges are required for the
.Xr chown 2
system call, otherwise 0.
.It Li _PC_NO_TRUNC
Return 1 if file names longer than KERN_NAME_MAX are truncated.
.It Li _PC_VDISABLE
Returns the terminal character disabling value.
.It Li _PC_XATTR_SIZE_BITS
Returns the number of bits used to store maximum extended 
attribute size in bytes.  For example, if the maximum 
attribute size supported by a file system is 128K, the 
value returned will be 18.  However a value 18 can mean 
that the maximum attribute size can be anywhere from 
(256KB - 1) to 128KB.  As a special case, the resource 
fork can have much larger size, and some file system 
specific extended attributes can have smaller and preset 
size; for example, Finder Info is always 32 bytes.
.It Li _PC_MIN_HOLE_SIZE
If a file system supports the reporting of holes (see
.Xr lseek 2 ) ,
.Fn pathconf
and
.Fn fpathconf
return a positive number that represents the minimum hole size returned in
bytes.
The offsets of holes returned will be aligned to this same value.
A special value of 1 is returned if the file system does not specify the minimum
hole size but still reports holes.
.El
.Sh RETURN VALUES
If the call to
.Nm pathconf
or
.Nm fpathconf
is not successful, \-1 is returned and
.Va errno
is set appropriately.
Otherwise, if the variable is associated with functionality that does
not have a limit in the system, \-1 is returned and
.Va errno
is not modified.
Otherwise, the current variable value is returned.
.Sh ERRORS
If any of the following conditions occur, the
.Nm pathconf
and
.Nm fpathconf
functions shall return -1 and set
.Va errno
to the corresponding value.
.Bl -tag -width ENAMETOOLONGAA
.\" ===========
.It Bq Er EINVAL
The value of the
.Fa name
argument is invalid.
.\" ===========
.It Bq Er EINVAL
The implementation does not support an association of the variable
name with the associated file.
.El
.Pp
.Fn pathconf
will fail if:
.Bl -tag -width ENAMETOOLONGAA
.\" ===========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ===========
.It Bq Er EIO
An I/O error occurs while reading from or writing to the file system.
.\" ===========
.It Bq Er ELOOP
Too many symbolic links are encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
.\" ===========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
.\" ===========
.It Bq Er ENOENT
The named file does not exist.
.\" ===========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.El
.Pp
.Bl -tag -width ENAMETOOLONGAA
.Fn fpathconf
will fail if:
.\" ===========
.It Bq Er EBADF
.Fa fildes
is not a valid open file descriptor.
.\" ===========
.It Bq Er EIO
An I/O error occurs while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr sysctl 3
.Sh HISTORY
The
.Nm pathconf
and
.Nm fpathconf
functions first appeared in 4.4BSD.
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1993
	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	.\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt PATHCONF 2
	38	.Os BSD 4
	39	.Sh NAME
2d21ac55 A	40	.Nm fpathconf ,
2d21ac55 A	41	.Nm pathconf
9bccf70c A	42	.Nd get configurable pathname variables
	43	.Sh SYNOPSIS
	44	.Fd #include <unistd.h>
	45	.Ft long
2d21ac55 A	46	.Fo fpathconf
	47	.Fa "int fildes"
	48	.Fa "int name"
	49	.Fc
9bccf70c	50	.Ft long
2d21ac55 A	51	.Fo pathconf
	52	.Fa "const char *path"
	53	.Fa "int name"
	54	.Fc
9bccf70c A	55	.Sh DESCRIPTION
	56	.Pp
	57	The
	58	.Fn pathconf
	59	and
	60	.Fn fpathconf
	61	functions provides a method for applications to determine the current
	62	value of a configurable system limit or option variable associated
	63	with a pathname or file descriptor.
	64	.Pp
	65	For
	66	.Nm pathconf ,
	67	the
	68	.Fa path
	69	argument is the name of a file or directory.
	70	For
	71	.Nm fpathconf ,
	72	the
2d21ac55	73	.Fa fildes
9bccf70c A	74	argument is an open file descriptor.
	75	The
	76	.Fa name
	77	argument specifies the system variable to be queried.
	78	Symbolic constants for each name value are found in the include file
	79	.Li <unistd.h> .
	80	.Pp
	81	The available values are as follows:
	82	.Pp
	83	.Bl -tag -width "123456"
	84	.Pp
	85	.It Li _PC_LINK_MAX
	86	The maximum file link count.
	87	.It Li _PC_MAX_CANON
	88	The maximum number of bytes in terminal canonical input line.
	89	.It Li _PC_MAX_INPUT
	90	The minimum maximum number of bytes for which space is available in
	91	a terminal input queue.
	92	.It Li _PC_NAME_MAX
	93	The maximum number of bytes in a file name.
	94	.It Li _PC_PATH_MAX
	95	The maximum number of bytes in a pathname.
	96	.It Li _PC_PIPE_BUF
	97	The maximum number of bytes which will be written atomically to a pipe.
	98	.It Li _PC_CHOWN_RESTRICTED
	99	Return 1 if appropriate privileges are required for the
	100	.Xr chown 2
	101	system call, otherwise 0.
	102	.It Li _PC_NO_TRUNC
	103	Return 1 if file names longer than KERN_NAME_MAX are truncated.
	104	.It Li _PC_VDISABLE
	105	Returns the terminal character disabling value.
6d2010ae A	106	.It Li _PC_XATTR_SIZE_BITS
	107	Returns the number of bits used to store maximum extended
	108	attribute size in bytes. For example, if the maximum
	109	attribute size supported by a file system is 128K, the
	110	value returned will be 18. However a value 18 can mean
	111	that the maximum attribute size can be anywhere from
	112	(256KB - 1) to 128KB. As a special case, the resource
	113	fork can have much larger size, and some file system
	114	specific extended attributes can have smaller and preset
	115	size; for example, Finder Info is always 32 bytes.
813fb2f6 A	116	.It Li _PC_MIN_HOLE_SIZE
	117	If a file system supports the reporting of holes (see
	118	.Xr lseek 2 ) ,
	119	.Fn pathconf
	120	and
	121	.Fn fpathconf
	122	return a positive number that represents the minimum hole size returned in
	123	bytes.
	124	The offsets of holes returned will be aligned to this same value.
	125	A special value of 1 is returned if the file system does not specify the minimum
	126	hole size but still reports holes.
9bccf70c A	127	.El
	128	.Sh RETURN VALUES
	129	If the call to
	130	.Nm pathconf
	131	or
	132	.Nm fpathconf
	133	is not successful, \-1 is returned and
	134	.Va errno
	135	is set appropriately.
	136	Otherwise, if the variable is associated with functionality that does
	137	not have a limit in the system, \-1 is returned and
	138	.Va errno
	139	is not modified.
	140	Otherwise, the current variable value is returned.
	141	.Sh ERRORS
	142	If any of the following conditions occur, the
	143	.Nm pathconf
	144	and
	145	.Nm fpathconf
	146	functions shall return -1 and set
	147	.Va errno
	148	to the corresponding value.
2d21ac55 A	149	.Bl -tag -width ENAMETOOLONGAA
2d21ac55 A	150	.\" ===========
9bccf70c A	151	.It Bq Er EINVAL
	152	The value of the
	153	.Fa name
	154	argument is invalid.
2d21ac55	155	.\" ===========
9bccf70c A	156	.It Bq Er EINVAL
	157	The implementation does not support an association of the variable
	158	name with the associated file.
	159	.El
2d21ac55	160	.Pp
39037602	161	.Fn pathconf
9bccf70c A	162	will fail if:
9bccf70c A	163	.Bl -tag -width ENAMETOOLONGAA
2d21ac55 A	164	.\" ===========
	165	.It Bq Er EACCES
	166	Search permission is denied for a component of the path prefix.
	167	.\" ===========
	168	.It Bq Er EIO
	169	An I/O error occurs while reading from or writing to the file system.
	170	.\" ===========
	171	.It Bq Er ELOOP
	172	Too many symbolic links are encountered in translating the pathname.
	173	This is taken to be indicative of a looping symbolic link.
	174	.\" ===========
9bccf70c A	175	.It Bq Er ENAMETOOLONG
	176	A component of a pathname exceeded 255 characters,
	177	or an entire path name exceeded 1023 characters.
2d21ac55	178	.\" ===========
9bccf70c A	179	.It Bq Er ENOENT
9bccf70c A	180	The named file does not exist.
2d21ac55 A	181	.\" ===========
	182	.It Bq Er ENOTDIR
	183	A component of the path prefix is not a directory.
9bccf70c A	184	.El
9bccf70c A	185	.Pp
2d21ac55	186	.Bl -tag -width ENAMETOOLONGAA
39037602	187	.Fn fpathconf
9bccf70c	188	will fail if:
2d21ac55	189	.\" ===========
9bccf70c	190	.It Bq Er EBADF
2d21ac55	191	.Fa fildes
9bccf70c	192	is not a valid open file descriptor.
2d21ac55	193	.\" ===========
9bccf70c	194	.It Bq Er EIO
2d21ac55	195	An I/O error occurs while reading from or writing to the file system.
9bccf70c A	196	.El
	197	.Sh SEE ALSO
	198	.Xr sysctl 3
	199	.Sh HISTORY
	200	The
	201	.Nm pathconf
	202	and
	203	.Nm fpathconf
	204	functions first appeared in 4.4BSD.