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 1.8.2.6 2001/12/14 18:33:51 ru Exp $ 34.\" $DragonFly: src/lib/libc/gen/sysconf.3,v 1.7 2008/05/02 02:05:03 swildner Exp $ 35.\" 36.Dd November 7, 2009 37.Dt SYSCONF 3 38.Os 39.Sh NAME 40.Nm sysconf 41.Nd get configurable system variables 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft long 47.Fn sysconf "int name" 48.Sh DESCRIPTION 49This interface is defined by 50.St -p1003.1-88 . 51A far more complete interface is available using 52.Xr sysctl 3 . 53.Pp 54The 55.Fn sysconf 56function provides a method for applications to determine the current 57value of a configurable system limit or option variable. 58The 59.Fa name 60argument specifies the system variable to be queried. 61Symbolic constants for each name value are found in the include file 62.In unistd.h . 63.Pp 64The available values are as follows: 65.Bl -tag -width 6n 66.It Li _SC_ARG_MAX 67The maximum bytes of argument to 68.Xr execve 2 . 69.It Li _SC_BC_BASE_MAX 70The maximum ibase/obase values in the 71.Xr bc 1 72utility. 73.It Li _SC_BC_DIM_MAX 74The maximum array size in the 75.Xr bc 1 76utility. 77.It Li _SC_BC_SCALE_MAX 78The maximum scale value in the 79.Xr bc 1 80utility. 81.It Li _SC_BC_STRING_MAX 82The maximum string length in the 83.Xr bc 1 84utility. 85.It Li _SC_CHILD_MAX 86The maximum number of simultaneous processes per user id. 87.It Li _SC_CLK_TCK 88The frequency of the statistics clock in ticks per second. 89.It Li _SC_COLL_WEIGHTS_MAX 90The maximum number of weights that can be assigned to any entry of 91the LC_COLLATE order keyword in the locale definition file. 92.It Li _SC_EXPR_NEST_MAX 93The maximum number of expressions that can be nested within 94parenthesis by the 95.Xr expr 1 96utility. 97.It Li _SC_IOV_MAX 98The maximum number of elements in the I/O vector used by 99.Xr readv 2 , 100.Xr writev 2 , 101.Xr recvmsg 2 , 102and 103.Xr sendmsg 2 . 104.It Li _SC_JOB_CONTROL 105Return 1 if job control is available on this system, otherwise \-1. 106.It Li _SC_LINE_MAX 107The maximum length in bytes of a text-processing utility's input 108line. 109.It Li _SC_MESSAGE_PASSING 110Whether Message Passing option is supported. 111.It Li _SC_MQ_OPEN_MAX 112The maximum number of open message queue descriptors per process. 113.It Li _SC_MQ_PRIO_MAX 114The maximum number of message priorities supported by the implementation. 115.It Li _SC_NGROUPS_MAX 116The maximum number of supplemental groups. 117.It Li _SC_NPROCESSORS_CONF 118The number of processors configured. 119.It Li _SC_NPROCESSORS_ONLN 120The number of processors online. 121.It Li _SC_OPEN_MAX 122The maximum number of open files per user id. 123.It Li _SC_PAGESIZE 124The size of a system page in bytes. 125.It Li _SC_RE_DUP_MAX 126The maximum number of repeated occurrences of a regular expression 127permitted when using interval notation. 128.It Li _SC_SAVED_IDS 129Returns 1 if saved set-group and saved set-user ID is available, 130otherwise \-1. 131.It Li _SC_STREAM_MAX 132The minimum maximum number of streams that a process may have open 133at any one time. 134.It Li _SC_TZNAME_MAX 135The minimum maximum number of types supported for the name of a 136timezone. 137.It Li _SC_VERSION 138The version of 139.St -p1003.1 140with which the system 141attempts to comply. 142.It Li _SC_2_C_BIND 143Return 1 if the system's C-language development facilities support the 144C-Language Bindings Option, otherwise \-1. 145.It Li _SC_2_C_DEV 146Return 1 if the system supports the C-Language Development Utilities Option, 147otherwise \-1. 148.It Li _SC_2_CHAR_TERM 149Return 1 if the system supports at least one terminal type capable of 150all operations described in 151.St -p1003.2 , 152otherwise \-1. 153.It Li _SC_2_FORT_DEV 154Return 1 if the system supports the FORTRAN Development Utilities Option, 155otherwise \-1. 156.It Li _SC_2_FORT_RUN 157Return 1 if the system supports the FORTRAN Runtime Utilities Option, 158otherwise \-1. 159.It Li _SC_2_LOCALEDEF 160Return 1 if the system supports the creation of locales, otherwise \-1. 161.It Li _SC_2_SW_DEV 162Return 1 if the system supports the Software Development Utilities Option, 163otherwise \-1. 164.It Li _SC_2_UPE 165Return 1 if the system supports the User Portability Utilities Option, 166otherwise \-1. 167.It Li _SC_2_VERSION 168The version of 169.St -p1003.2 170with which the system attempts to comply. 171.El 172.Sh RETURN VALUES 173If the call to 174.Fn sysconf 175is not successful, \-1 is returned and 176.Va errno 177is set appropriately. 178Otherwise, if the variable is associated with functionality that is not 179supported, \-1 is returned and 180.Va errno 181is not modified. 182Otherwise, the current variable value is returned. 183.Sh ERRORS 184The 185.Fn sysconf 186function may fail and set 187.Va errno 188for any of the errors specified for the library function 189.Xr sysctl 3 . 190In addition, the following error may be reported: 191.Bl -tag -width Er 192.It Bq Er EINVAL 193The value of the 194.Fa name 195argument is invalid. 196.El 197.Sh SEE ALSO 198.Xr sysctl 3 199.Sh STANDARDS 200Except for the fact that values returned by 201.Fn sysconf 202may change over the lifetime of the calling process, 203this function conforms to 204.St -p1003.1-88 . 205.Pp 206_SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are nonstandard, but implemented 207in many systems. 208.Sh HISTORY 209The 210.Fn sysconf 211function first appeared in 212.Bx 4.4 . 213.Sh BUGS 214The value for _SC_STREAM_MAX is a minimum maximum, and required to be 215the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 216small and misleading number. 217