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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 29.\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.8.2.6 2001/12/14 18:33:51 ru Exp $ 30.\" 31.Dd October 26, 2015 32.Dt SYSCONF 3 33.Os 34.Sh NAME 35.Nm sysconf 36.Nd get configurable system variables 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft long 42.Fn sysconf "int name" 43.Sh DESCRIPTION 44This interface is defined by 45.St -p1003.1-88 . 46A far more complete interface is available using 47.Xr sysctl 3 . 48.Pp 49The 50.Fn sysconf 51function provides a method for applications to determine the current 52value of a configurable system limit or option variable. 53The 54.Fa name 55argument specifies the system variable to be queried. 56Symbolic constants for each name value are found in the include file 57.In unistd.h . 58.Pp 59The available values are as follows: 60.Bl -tag -width 6n 61.It Li _SC_ARG_MAX 62The maximum bytes of argument to 63.Xr execve 2 . 64.It Li _SC_BC_BASE_MAX 65The maximum ibase/obase values in the 66.Xr bc 1 67utility. 68.It Li _SC_BC_DIM_MAX 69The maximum array size in the 70.Xr bc 1 71utility. 72.It Li _SC_BC_SCALE_MAX 73The maximum scale value in the 74.Xr bc 1 75utility. 76.It Li _SC_BC_STRING_MAX 77The maximum string length in the 78.Xr bc 1 79utility. 80.It Li _SC_CHILD_MAX 81The maximum number of simultaneous processes per user id. 82.It Li _SC_CLK_TCK 83The frequency of the statistics clock in ticks per second. 84.It Li _SC_COLL_WEIGHTS_MAX 85The maximum number of weights that can be assigned to any entry of 86the LC_COLLATE order keyword in the locale definition file. 87.It Li _SC_EXPR_NEST_MAX 88The maximum number of expressions that can be nested within 89parenthesis by the 90.Xr expr 1 91utility. 92.It Li _SC_IOV_MAX 93The maximum number of elements in the I/O vector used by 94.Xr readv 2 , 95.Xr writev 2 , 96.Xr recvmsg 2 , 97and 98.Xr sendmsg 2 . 99.It Li _SC_JOB_CONTROL 100Return 1 if job control is available on this system, otherwise \-1. 101.It Li _SC_LINE_MAX 102The maximum length in bytes of a text-processing utility's input 103line. 104.It Li _SC_MESSAGE_PASSING 105Whether Message Passing option is supported. 106.It Li _SC_MQ_OPEN_MAX 107The maximum number of open message queue descriptors per process. 108.It Li _SC_MQ_PRIO_MAX 109The maximum number of message priorities supported by the implementation. 110.It Li _SC_NGROUPS_MAX 111The maximum number of supplemental groups. 112.It Li _SC_NPROCESSORS_CONF 113The number of processors configured. 114.It Li _SC_NPROCESSORS_ONLN 115The number of processors online. 116.It Li _SC_OPEN_MAX 117The maximum number of open files per user id. 118.It Li _SC_PAGESIZE 119The size of a system page in bytes. 120.It Li _SC_RE_DUP_MAX 121The maximum number of repeated occurrences of a regular expression 122permitted when using interval notation. 123.It Li _SC_SAVED_IDS 124Returns 1 if saved set-group and saved set-user ID is available, 125otherwise \-1. 126.It Li _SC_STREAM_MAX 127The minimum maximum number of streams that a process may have open 128at any one time. 129.It Li _SC_TZNAME_MAX 130The minimum maximum number of types supported for the name of a 131timezone. 132.It Li _SC_VERSION 133The version of 134.St -p1003.1 135with which the system 136attempts to comply. 137.It Li _SC_XOPEN_SHM 138Return 1 if the system supports the 139.St -xpg4.2 140Shared Memory Feature 141for both compilation and execution, or 0 if only compilation support is 142guaranteed. 143.It Li _SC_2_C_BIND 144Return 1 if the system's C-language development facilities support the 145C-Language Bindings Option, otherwise \-1. 146.It Li _SC_2_C_DEV 147Return 1 if the system supports the C-Language Development Utilities Option, 148otherwise \-1. 149.It Li _SC_2_CHAR_TERM 150Return 1 if the system supports at least one terminal type capable of 151all operations described in 152.St -p1003.2 , 153otherwise \-1. 154.It Li _SC_2_FORT_DEV 155Return 1 if the system supports the FORTRAN Development Utilities Option, 156otherwise \-1. 157.It Li _SC_2_FORT_RUN 158Return 1 if the system supports the FORTRAN Runtime Utilities Option, 159otherwise \-1. 160.It Li _SC_2_LOCALEDEF 161Return 1 if the system supports the creation of locales, otherwise \-1. 162.It Li _SC_2_SW_DEV 163Return 1 if the system supports the Software Development Utilities Option, 164otherwise \-1. 165.It Li _SC_2_UPE 166Return 1 if the system supports the User Portability Utilities Option, 167otherwise \-1. 168.It Li _SC_2_VERSION 169The version of 170.St -p1003.2 171with which the system attempts to comply. 172.El 173.Sh RETURN VALUES 174If the call to 175.Fn sysconf 176is not successful, \-1 is returned and 177.Va errno 178is set appropriately. 179Otherwise, if the variable is associated with functionality that is not 180supported, \-1 is returned and 181.Va errno 182is not modified. 183Otherwise, the current variable value is returned. 184.Sh ERRORS 185The 186.Fn sysconf 187function may fail and set 188.Va errno 189for any of the errors specified for the library function 190.Xr sysctl 3 . 191In addition, the following error may be reported: 192.Bl -tag -width Er 193.It Bq Er EINVAL 194The value of the 195.Fa name 196argument is invalid. 197.El 198.Sh SEE ALSO 199.Xr sysctl 3 200.Sh STANDARDS 201Except for the fact that values returned by 202.Fn sysconf 203may change over the lifetime of the calling process, 204this function conforms to 205.St -p1003.1-88 . 206.Pp 207_SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are nonstandard, but implemented 208in many systems. 209.Sh HISTORY 210The 211.Fn sysconf 212function first appeared in 213.Bx 4.4 . 214.Sh BUGS 215The value for _SC_STREAM_MAX is a minimum maximum, and required to be 216the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 217small and misleading number. 218