[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_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.
88	.It Li _SC_STREAM_MAX
89	The minimum maximum number of streams that a process may have open
90	at any one time.
91	.It Li _SC_TZNAME_MAX
92	The minimum maximum number of types supported for the name of a
93	timezone.
94	.It Li _SC_JOB_CONTROL
95	Return 1 if job control is available on this system, otherwise \-1.
96	.It Li _SC_SAVED_IDS
97	Returns 1 if saved set-group and saved set-user ID is available,
98	otherwise \-1.
99	.It Li _SC_VERSION
100	The version of
101	.St -p1003.1
102	with which the system
103	attempts to comply.
104	.It Li _SC_BC_BASE_MAX
105	The maximum ibase/obase values in the
106	.Xr bc 1
107	utility.
108	.It Li _SC_BC_DIM_MAX
109	The maximum array size in the
110	.Xr bc 1
111	utility.
112	.It Li _SC_BC_SCALE_MAX
113	The maximum scale value in the
114	.Xr bc 1
115	utility.
116	.It Li _SC_BC_STRING_MAX
117	The maximum string length in the
118	.Xr bc 1
119	utility.
120	.It Li _SC_COLL_WEIGHTS_MAX
121	The maximum number of weights that can be assigned to any entry of
122	the LC_COLLATE order keyword in the locale definition file.
123	.It Li _SC_EXPR_NEST_MAX
124	The maximum number of expressions that can be nested within
125	parenthesis by the
126	.Xr expr 1
127	utility.
128	.It Li _SC_LINE_MAX
129	The maximum length in bytes of a text-processing utility's input
130	line.
131	.It Li _SC_RE_DUP_MAX
132	The maximum number of repeated occurrences of a regular expression
133	permitted when using interval notation.
134	.It Li _SC_2_VERSION
135	The version of
136	.St -p1003.2
137	with which the system attempts to comply.
138	.It Li _SC_2_C_BIND
139	Return 1 if the system's C-language development facilities support the
140	C-Language Bindings Option, otherwise \-1.
141	.It Li _SC_2_C_DEV
142	Return 1 if the system supports the C-Language Development Utilities Option,
143	otherwise \-1.
144	.It Li _SC_2_CHAR_TERM
145	Return 1 if the system supports at least one terminal type capable of
146	all operations described in
147	.St -p1003.2 ,
148	otherwise \-1.
149	.It Li _SC_2_FORT_DEV
150	Return 1 if the system supports the FORTRAN Development Utilities Option,
151	otherwise \-1.
152	.It Li _SC_2_FORT_RUN
153	Return 1 if the system supports the FORTRAN Runtime Utilities Option,
154	otherwise \-1.
155	.It Li _SC_2_LOCALEDEF
156	Return 1 if the system supports the creation of locales, otherwise \-1.
157	.It Li _SC_2_SW_DEV
158	Return 1 if the system supports the Software Development Utilities Option,
159	otherwise \-1.
160	.It Li _SC_2_UPE
161	Return 1 if the system supports the User Portability Utilities Option,
162	otherwise \-1.
163	.El
164	.Sh RETURN VALUES
165	If the call to
166	.Fn sysconf
167	is not successful, \-1 is returned and
168	.Va errno
169	is set appropriately.
170	Otherwise, if the variable is associated with functionality that is not
171	supported, \-1 is returned and
172	.Va errno
173	is not modified.
174	Otherwise, the current variable value is returned.
175	.Sh ERRORS
176	The
177	.Fn sysconf
178	function may fail and set
179	.Va errno
180	for any of the errors specified for the library function
181	.Xr sysctl 3 .
182	In addition, the following error may be reported:
183	.Bl -tag -width Er
184	.It Bq Er EINVAL
185	The value of the
186	.Fa name
187	argument is invalid.
188	.El
189	.Sh SEE ALSO
190	.Xr getconf 1 ,
191	.Xr pathconf 2 ,
192	.Xr confstr 3 ,
193	.Xr sysctl 3
194	.Sh BUGS
195	The value for _SC_STREAM_MAX is a minimum maximum, and required to be
196	the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
197	small and misleading number.
198	.Sh STANDARDS
199	Except for the fact that values returned by
200	.Fn sysconf
201	may change over the lifetime of the calling process,
202	this function conforms to
203	.St -p1003.1-88 .
204	.Sh HISTORY
205	The
206	.Fn sysconf
207	function first appeared in
208	.Bx 4.4 .