[apple/libc.git] / gen / sysconf.3

.\" 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.
.\"
.\"	@(#)sysconf.3	8.3 (Berkeley) 4/19/94
.\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.16 2001/10/01 16:08:51 ru Exp $
.\"
.Dd June 18, 2001
.Dt SYSCONF 3
.Os
.Sh NAME
.Nm sysconf
.Nd get configurable system variables
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft long
.Fn sysconf "int name"
.Sh DESCRIPTION
This interface is defined by
.St -p1003.1-88 .
A far more complete interface is available using
.Xr sysctl 3 .
.Pp
The
.Fn sysconf
function provides a method for applications to determine the current
value of a configurable system limit or option variable.
The
.Fa name
argument specifies the system variable to be queried.
Symbolic constants for each name value are found in the include file
.Aq Pa unistd.h .
Shell programmers who need access to these parameters should use the
.Xr getconf 1
utility.
.Pp
The available values are as follows:
.Pp
.Bl -tag -width 6n
.Pp
.It Li _SC_ARG_MAX
The maximum bytes of argument to
.Xr execve 2 .
.It Li _SC_CHILD_MAX
The maximum number of simultaneous processes per user id.
.It Li _SC_CLK_TCK
The frequency of the statistics clock in ticks per second.
.It Li _SC_IOV_MAX
The maximum number of elements in the I/O vector used by
.Xr readv 2 ,
.Xr writev 2 ,
.Xr recvmsg 2 ,
and
.Xr sendmsg 2 .
.It Li _SC_NGROUPS_MAX
The maximum number of supplemental groups.
.It Li _SC_OPEN_MAX
The maximum number of open files per user id.
.It Li _SC_PAGESIZE
The memory page size of the system expressed in bytes.
This is the fundamental unit of memory management of the operating system.
.It Li _SC_STREAM_MAX
The minimum maximum number of streams that a process may have open
at any one time.
.It Li _SC_TZNAME_MAX
The minimum maximum number of types supported for the name of a
timezone.
.It Li _SC_JOB_CONTROL
Return 1 if job control is available on this system, otherwise \-1.
.It Li _SC_SAVED_IDS
Returns 1 if saved set-group and saved set-user ID is available,
otherwise \-1.
.It Li _SC_VERSION
The version of
.St -p1003.1
with which the system
attempts to comply.
.It Li _SC_BC_BASE_MAX
The maximum ibase/obase values in the
.Xr bc 1
utility.
.It Li _SC_BC_DIM_MAX
The maximum array size in the
.Xr bc 1
utility.
.It Li _SC_BC_SCALE_MAX
The maximum scale value in the
.Xr bc 1
utility.
.It Li _SC_BC_STRING_MAX
The maximum string length in the
.Xr bc 1
utility.
.It Li _SC_COLL_WEIGHTS_MAX
The maximum number of weights that can be assigned to any entry of
the LC_COLLATE order keyword in the locale definition file.
.It Li _SC_EXPR_NEST_MAX
The maximum number of expressions that can be nested within
parenthesis by the
.Xr expr 1
utility.
.It Li _SC_LINE_MAX
The maximum length in bytes of a text-processing utility's input
line.
.It Li _SC_RE_DUP_MAX
The maximum number of repeated occurrences of a regular expression
permitted when using interval notation.
.It Li _SC_2_VERSION
The version of
.St -p1003.2
with which the system attempts to comply.
.It Li _SC_2_C_BIND
Return 1 if the system's C-language development facilities support the
C-Language Bindings Option, otherwise \-1.
.It Li _SC_2_C_DEV
Return 1 if the system supports the C-Language Development Utilities Option,
otherwise \-1.
.It Li _SC_2_CHAR_TERM
Return 1 if the system supports at least one terminal type capable of
all operations described in
.St -p1003.2 ,
otherwise \-1.
.It Li _SC_2_FORT_DEV
Return 1 if the system supports the FORTRAN Development Utilities Option,
otherwise \-1.
.It Li _SC_2_FORT_RUN
Return 1 if the system supports the FORTRAN Runtime Utilities Option,
otherwise \-1.
.It Li _SC_2_LOCALEDEF
Return 1 if the system supports the creation of locales, otherwise \-1.
.It Li _SC_2_SW_DEV
Return 1 if the system supports the Software Development Utilities Option,
otherwise \-1.
.It Li _SC_2_UPE
Return 1 if the system supports the User Portability Utilities Option,
otherwise \-1.
.El
.Sh RETURN VALUES
If the call to
.Fn sysconf
is not successful, \-1 is returned and
.Va errno
is set appropriately.
Otherwise, if the variable is associated with functionality that is not
supported, \-1 is returned and
.Va errno
is not modified.
Otherwise, the current variable value is returned.
.Sh ERRORS
The
.Fn sysconf
function may fail and set
.Va errno
for any of the errors specified for the library function
.Xr sysctl 3 .
In addition, the following error may be reported:
.Bl -tag -width Er
.It Bq Er EINVAL
The value of the
.Fa name
argument is invalid.
.El
.Sh SEE ALSO
.Xr getconf 1 ,
.Xr pathconf 2 ,
.Xr confstr 3 ,
.Xr sysctl 3
.Sh BUGS
The value for _SC_STREAM_MAX is a minimum maximum, and required to be
the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
small and misleading number.
.Sh STANDARDS
Except for the fact that values returned by
.Fn sysconf
may change over the lifetime of the calling process,
this function conforms to
.St -p1003.1-88 .
.Sh HISTORY
The
.Fn sysconf
function first appeared in
.Bx 4.4 .
Commit	Line	Data
5b2abdfb A	1	.\" Copyright (c) 1993
	2	.\" The Regents of the University of California. 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	.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94
	33	.\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.16 2001/10/01 16:08:51 ru Exp $
	34	.\"
	35	.Dd June 18, 2001
	36	.Dt SYSCONF 3
	37	.Os
	38	.Sh NAME
	39	.Nm sysconf
	40	.Nd get configurable system variables
	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
	44	.In unistd.h
	45	.Ft long
	46	.Fn sysconf "int name"
	47	.Sh DESCRIPTION
	48	This interface is defined by
	49	.St -p1003.1-88 .
	50	A far more complete interface is available using
	51	.Xr sysctl 3 .
	52	.Pp
	53	The
	54	.Fn sysconf
	55	function provides a method for applications to determine the current
	56	value of a configurable system limit or option variable.
	57	The
	58	.Fa name
	59	argument specifies the system variable to be queried.
	60	Symbolic constants for each name value are found in the include file
	61	.Aq Pa unistd.h .
	62	Shell programmers who need access to these parameters should use the
	63	.Xr getconf 1
	64	utility.
65	.Pp
66	The available values are as follows:
67	.Pp
68	.Bl -tag -width 6n
69	.Pp
70	.It Li _SC_ARG_MAX
71	The maximum bytes of argument to
72	.Xr execve 2 .
73	.It Li _SC_CHILD_MAX
74	The maximum number of simultaneous processes per user id.
75	.It Li _SC_CLK_TCK
76	The frequency of the statistics clock in ticks per second.
77	.It Li _SC_IOV_MAX
78	The maximum number of elements in the I/O vector used by
79	.Xr readv 2 ,
80	.Xr writev 2 ,
81	.Xr recvmsg 2 ,
82	and
83	.Xr sendmsg 2 .
84	.It Li _SC_NGROUPS_MAX
85	The maximum number of supplemental groups.
86	.It Li _SC_OPEN_MAX
87	The maximum number of open files per user id.
9385eb3d A	88	.It Li _SC_PAGESIZE
	89	The memory page size of the system expressed in bytes.
	90	This is the fundamental unit of memory management of the operating system.
5b2abdfb A	91	.It Li _SC_STREAM_MAX
	92	The minimum maximum number of streams that a process may have open
	93	at any one time.
	94	.It Li _SC_TZNAME_MAX
	95	The minimum maximum number of types supported for the name of a
	96	timezone.
	97	.It Li _SC_JOB_CONTROL
	98	Return 1 if job control is available on this system, otherwise \-1.
	99	.It Li _SC_SAVED_IDS
	100	Returns 1 if saved set-group and saved set-user ID is available,
	101	otherwise \-1.
	102	.It Li _SC_VERSION
	103	The version of
	104	.St -p1003.1
	105	with which the system
	106	attempts to comply.
	107	.It Li _SC_BC_BASE_MAX
	108	The maximum ibase/obase values in the
	109	.Xr bc 1
	110	utility.
	111	.It Li _SC_BC_DIM_MAX
	112	The maximum array size in the
	113	.Xr bc 1
	114	utility.
	115	.It Li _SC_BC_SCALE_MAX
	116	The maximum scale value in the
	117	.Xr bc 1
	118	utility.
	119	.It Li _SC_BC_STRING_MAX
	120	The maximum string length in the
	121	.Xr bc 1
	122	utility.
	123	.It Li _SC_COLL_WEIGHTS_MAX
	124	The maximum number of weights that can be assigned to any entry of
	125	the LC_COLLATE order keyword in the locale definition file.
	126	.It Li _SC_EXPR_NEST_MAX
	127	The maximum number of expressions that can be nested within
	128	parenthesis by the
	129	.Xr expr 1
	130	utility.
	131	.It Li _SC_LINE_MAX
	132	The maximum length in bytes of a text-processing utility's input
	133	line.
	134	.It Li _SC_RE_DUP_MAX
	135	The maximum number of repeated occurrences of a regular expression
	136	permitted when using interval notation.
	137	.It Li _SC_2_VERSION
	138	The version of
	139	.St -p1003.2
	140	with which the system attempts to comply.
	141	.It Li _SC_2_C_BIND
	142	Return 1 if the system's C-language development facilities support the
	143	C-Language Bindings Option, otherwise \-1.
	144	.It Li _SC_2_C_DEV
	145	Return 1 if the system supports the C-Language Development Utilities Option,
	146	otherwise \-1.
	147	.It Li _SC_2_CHAR_TERM
	148	Return 1 if the system supports at least one terminal type capable of
	149	all operations described in
	150	.St -p1003.2 ,
	151	otherwise \-1.
	152	.It Li _SC_2_FORT_DEV
	153	Return 1 if the system supports the FORTRAN Development Utilities Option,
	154	otherwise \-1.
155	.It Li _SC_2_FORT_RUN
156	Return 1 if the system supports the FORTRAN Runtime Utilities Option,
157	otherwise \-1.
158	.It Li _SC_2_LOCALEDEF
159	Return 1 if the system supports the creation of locales, otherwise \-1.
160	.It Li _SC_2_SW_DEV
161	Return 1 if the system supports the Software Development Utilities Option,
162	otherwise \-1.
163	.It Li _SC_2_UPE
164	Return 1 if the system supports the User Portability Utilities Option,
165	otherwise \-1.
166	.El
167	.Sh RETURN VALUES
168	If the call to
169	.Fn sysconf
170	is not successful, \-1 is returned and
171	.Va errno
172	is set appropriately.
173	Otherwise, if the variable is associated with functionality that is not
174	supported, \-1 is returned and
175	.Va errno
176	is not modified.
177	Otherwise, the current variable value is returned.
178	.Sh ERRORS
179	The
180	.Fn sysconf
181	function may fail and set
182	.Va errno
183	for any of the errors specified for the library function
184	.Xr sysctl 3 .
185	In addition, the following error may be reported:
186	.Bl -tag -width Er
187	.It Bq Er EINVAL
188	The value of the
189	.Fa name
190	argument is invalid.
191	.El
192	.Sh SEE ALSO
193	.Xr getconf 1 ,
194	.Xr pathconf 2 ,
195	.Xr confstr 3 ,
196	.Xr sysctl 3
197	.Sh BUGS
198	The value for _SC_STREAM_MAX is a minimum maximum, and required to be
199	the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
200	small and misleading number.
201	.Sh STANDARDS
202	Except for the fact that values returned by
203	.Fn sysconf
204	may change over the lifetime of the calling process,
205	this function conforms to
206	.St -p1003.1-88 .
207	.Sh HISTORY
208	The
209	.Fn sysconf
210	function first appeared in
211	.Bx 4.4 .