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 December 19, 2017 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 Dv _SC_ARG_MAX 62The maximum bytes of argument to 63.Xr execve 2 . 64.It Dv _SC_BC_BASE_MAX 65The maximum ibase/obase values in the 66.Xr bc 1 67utility. 68.It Dv _SC_BC_DIM_MAX 69The maximum array size in the 70.Xr bc 1 71utility. 72.It Dv _SC_BC_SCALE_MAX 73The maximum scale value in the 74.Xr bc 1 75utility. 76.It Dv _SC_BC_STRING_MAX 77The maximum string length in the 78.Xr bc 1 79utility. 80.It Dv _SC_CHILD_MAX 81The maximum number of simultaneous processes per user id. 82.It Dv _SC_CLK_TCK 83The frequency of the statistics clock in ticks per second. 84.It Dv _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 Dv _SC_EXPR_NEST_MAX 88The maximum number of expressions that can be nested within 89parenthesis by the 90.Xr expr 1 91utility. 92.It Dv _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 Dv _SC_JOB_CONTROL 100Return 1 if job control is available on this system, otherwise \-1. 101.It Dv _SC_LEVEL1_DCACHE_LINESIZE 102Returns the L1 cache line size. 103.It Dv _SC_LINE_MAX 104The maximum length in bytes of a text-processing utility's input 105line. 106.It Dv _SC_MESSAGE_PASSING 107Whether Message Passing option is supported. 108.It Dv _SC_MQ_OPEN_MAX 109The maximum number of open message queue descriptors per process. 110.It Dv _SC_MQ_PRIO_MAX 111The maximum number of message priorities supported by the implementation. 112.It Dv _SC_NGROUPS_MAX 113The maximum number of supplemental groups. 114.It Dv _SC_NPROCESSORS_CONF 115The number of processors configured. 116.It Dv _SC_NPROCESSORS_ONLN 117The number of processors online. 118.It Dv _SC_OPEN_MAX 119The maximum number of open files per user id. 120.It Dv _SC_PAGESIZE 121The size of a system page in bytes. 122.It Dv _SC_PAGE_SIZE 123Equivalent to 124.Dv _SC_PAGESIZE . 125.It Dv _SC_RE_DUP_MAX 126The maximum number of repeated occurrences of a regular expression 127permitted when using interval notation. 128.It Dv _SC_REGEXP 129Return 1 if the system supports regular expression handling. 130.It Dv _SC_SAVED_IDS 131Return 1 if saved set-group and saved set-user ID is available, 132otherwise \-1. 133.It Dv _SC_SHELL 134Return 1 if the system supports the 135.Tn POSIX 136shell. 137.It Dv _SC_STREAM_MAX 138The minimum maximum number of streams that a process may have open 139at any one time. 140.It Dv _SC_TZNAME_MAX 141The minimum maximum number of types supported for the name of a 142timezone. 143.It Dv _SC_VERSION 144The version of 145.St -p1003.1 146with which the system 147attempts to comply. 148.It Dv _SC_XOPEN_SHM 149Return 1 if the system supports the 150.St -xpg4.2 151Shared Memory Feature 152for both compilation and execution, or 0 if only compilation support is 153guaranteed. 154.It Dv _SC_2_C_BIND 155Return 1 if the system's C-language development facilities support the 156C-Language Bindings Option, otherwise \-1. 157.It Dv _SC_2_C_DEV 158Return 1 if the system supports the C-Language Development Utilities Option, 159otherwise \-1. 160.It Dv _SC_2_CHAR_TERM 161Return 1 if the system supports at least one terminal type capable of 162all operations described in 163.St -p1003.2 , 164otherwise \-1. 165.It Dv _SC_2_FORT_DEV 166Return 1 if the system supports the FORTRAN Development Utilities Option, 167otherwise \-1. 168.It Dv _SC_2_FORT_RUN 169Return 1 if the system supports the FORTRAN Runtime Utilities Option, 170otherwise \-1. 171.It Dv _SC_2_LOCALEDEF 172Return 1 if the system supports the creation of locales, otherwise \-1. 173.It Dv _SC_2_SW_DEV 174Return 1 if the system supports the Software Development Utilities Option, 175otherwise \-1. 176.It Dv _SC_2_UPE 177Return 1 if the system supports the User Portability Utilities Option, 178otherwise \-1. 179.It Dv _SC_2_VERSION 180The version of 181.St -p1003.2 182with which the system attempts to comply. 183.El 184.Pp 185These values also exist, but may not be standard: 186.Bl -tag -width 6n 187.It Dv _SC_PHYS_PAGES 188The number of pages of physical memory. 189.El 190.Sh RETURN VALUES 191If the call to 192.Fn sysconf 193is not successful, \-1 is returned and 194.Va errno 195is set appropriately. 196Otherwise, if the variable is associated with functionality that is not 197supported, \-1 is returned and 198.Va errno 199is not modified. 200Otherwise, the current variable value is returned. 201.Sh ERRORS 202The 203.Fn sysconf 204function may fail and set 205.Va errno 206for any of the errors specified for the library function 207.Xr sysctl 3 . 208In addition, the following error may be reported: 209.Bl -tag -width Er 210.It Bq Er EINVAL 211The value of the 212.Fa name 213argument is invalid. 214.El 215.Sh SEE ALSO 216.Xr sysctl 3 217.Sh STANDARDS 218Except for the fact that values returned by 219.Fn sysconf 220may change over the lifetime of the calling process, 221this function conforms to 222.St -p1003.1-88 . 223.Pp 224.Dv _SC_NPROCESSORS_CONF 225and 226.Dv _SC_NPROCESSORS_ONLN 227are nonstandard, but implemented in many systems. 228.Sh HISTORY 229The 230.Fn sysconf 231function first appeared in 232.Bx 4.4 . 233.Sh BUGS 234The value for 235.Dv _SC_STREAM_MAX 236is a minimum maximum, and required to be the same as ANSI C's 237.Dv FOPEN_MAX , 238so the returned value is a ridiculously small and misleading number. 239