1.\" $OpenBSD: sysconf.3,v 1.35 2019/08/11 15:48:08 deraadt Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: August 11 2019 $ 31.Dt SYSCONF 3 32.Os 33.Sh NAME 34.Nm sysconf 35.Nd get configurable system variables 36.Sh SYNOPSIS 37.In unistd.h 38.Ft long 39.Fn sysconf "int name" 40.Sh DESCRIPTION 41The 42.Fn sysconf 43function provides a method for applications to determine the current 44value of a configurable system limit or option variable. 45The 46.Fa name 47argument specifies the system variable to be queried. 48Symbolic constants for each name value are found in the include file 49.In unistd.h . 50.Pp 51The available values are as follows: 52.Bl -tag -width "123456" 53.It Li _SC_ARG_MAX 54The maximum bytes of arguments to 55.Xr execve 2 56(including the environment). 57.It Li _SC_CHILD_MAX 58The maximum number of simultaneous processes per user ID. 59.It Li _SC_CLK_TCK 60The number of clock ticks per second. 61.It Li _SC_NGROUPS_MAX 62The maximum number of supplemental groups. 63.It Li _SC_OPEN_MAX 64The maximum number of open files per user ID. 65.It Li _SC_STREAM_MAX 66The minimum maximum number of streams that a process may have open 67at any one time. 68.It Li _SC_TZNAME_MAX 69The minimum maximum number of types supported for the name of a 70time zone. 71.It Li _SC_JOB_CONTROL 72Returns 1 if job control is available on this system, otherwise \-1. 73.It Li _SC_SAVED_IDS 74Returns 1 if saved set-group-ID and saved set-user-ID is available, 75otherwise \-1. 76.It Li _SC_VERSION 77The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 78attempts to comply. 79.It Li _SC_BC_BASE_MAX 80The maximum ibase/obase values in the 81.Xr bc 1 82utility. 83.It Li _SC_BC_DIM_MAX 84The maximum array size in the 85.Xr bc 1 86utility. 87.It Li _SC_BC_SCALE_MAX 88The maximum scale value in the 89.Xr bc 1 90utility. 91.It Li _SC_BC_STRING_MAX 92The maximum string length in the 93.Xr bc 1 94utility. 95.It Li _SC_COLL_WEIGHTS_MAX 96The maximum number of weights that can be assigned to any entry of 97the LC_COLLATE order keyword in the locale definition file. 98.It Li _SC_EXPR_NEST_MAX 99The maximum number of expressions that can be nested within 100parentheses by the 101.Xr expr 1 102utility. 103.It Li _SC_LINE_MAX 104The maximum length in bytes of a text-processing utility's input 105line. 106.It Li _SC_RE_DUP_MAX 107The maximum number of repeated occurrences of a regular expression 108permitted when using interval notation. 109.It Li _SC_2_VERSION 110The version of POSIX 1003.2 with which the system attempts to comply. 111.It Li _SC_2_C_BIND 112Return 1 if the system's C-language development facilities support the 113C-Language Bindings Option, otherwise \-1. 114.It Li _SC_2_C_DEV 115Return 1 if the system supports the C-Language Development Utilities Option, 116otherwise \-1. 117.It Li _SC_2_CHAR_TERM 118Return 1 if the system supports at least one terminal type capable of 119all operations described in POSIX 1003.2, otherwise \-1. 120.It Li _SC_2_FORT_DEV 121Return 1 if the system supports the FORTRAN Development Utilities Option, 122otherwise \-1. 123.It Li _SC_2_FORT_RUN 124Return 1 if the system supports the FORTRAN Runtime Utilities Option, 125otherwise \-1. 126.It Li _SC_2_LOCALEDEF 127Return 1 if the system supports the creation of locales, otherwise \-1. 128.It Li _SC_2_SW_DEV 129Return 1 if the system supports the Software Development Utilities Option, 130otherwise \-1. 131.It Li _SC_2_UPE 132Return 1 if the system supports the User Portability Utilities Option, 133otherwise \-1. 134.It Li _SC_PAGESIZE 135The size of a system page in bytes. 136.It Li _SC_FSYNC 137Return 1 if the system supports the File Synchronisation Option, otherwise \-1. 138.It Li _SC_XOPEN_SHM 139Return 1 if the system supports the Shared Memory Option, otherwise \-1. 140.It Li _SC_SEM_NSEMS_MAX 141The maximum number of semaphores in the system or \-1 if the system 142does not support the Semaphores Option. 143.It Li _SC_SEM_VALUE_MAX 144The maximum value a semaphore may have or \-1 if the system 145does not support the Semaphores Option. 146.It Li _SC_PHYS_PAGES 147The number of pages of physical memory. 148.It Li _SC_AVPHYS_PAGES 149The number of pages of physical memory not currently in use by the system. 150.It Li _SC_GETGR_R_SIZE_MAX 151The maximum size of the data buffer for the 152.Fn getgrgid_r 153and 154.Fn getgrnam_r 155functions. 156.It Li _SC_GETPW_R_SIZE_MAX 157The maximum size of the data buffer for the 158.Fn getpwuid_r 159and 160.Fn getpwnam_r 161functions. 162.It Li _SC_LOGIN_NAME_MAX 163The maximum length of a login name. 164.It Li _SC_THREAD_SAFE_FUNCTIONS 165The level of support for thread-safe (re-entrant) functions. 166.It Li _SC_NPROCESSORS_CONF 167The number of processors configured. 168.It Li _SC_NPROCESSORS_ONLN 169The number of processors online (capable of running processes). 170.It Li _SC_HOST_NAME_MAX 171The maximum size of a hostname, not counting NULL. 172.It Li _SC_MONOTONIC_CLOCK 173Return the POSIX version of the implementation of the Monotonic Clock 174option that this system conforms to, or \-1 if unavailable. 175.El 176.Sh RETURN VALUES 177If the call to 178.Fn sysconf 179is not successful, \-1 is returned and 180.Va errno 181is set appropriately. 182Otherwise, if the variable is associated with functionality that is not 183supported, \-1 is returned and 184.Va errno 185is not modified. 186Otherwise, the current variable value is returned. 187.Sh ERRORS 188The 189.Fn sysconf 190function may fail and set 191.Va errno 192for any of the errors specified for the library function 193.Xr sysctl 2 . 194In addition, the following error may be reported: 195.Bl -tag -width Er 196.It Bq Er EINVAL 197The value of the 198.Fa name 199argument is invalid. 200.El 201.Sh SEE ALSO 202.Xr pathconf 2 , 203.Xr sysctl 2 204.Sh STANDARDS 205The 206.Fn sysconf 207function conforms to 208.St -p1003.1-88 . 209The constants 210.Li _SC_NPROCESSORS_CONF 211and 212.Li _SC_NPROCESSORS_ONLN 213are not part of the standard, but are provided by many systems. 214.Sh HISTORY 215The 216.Fn sysconf 217function first appeared in 218.Bx 4.4 . 219.Sh BUGS 220The value for _SC_STREAM_MAX is a minimum maximum, and required to be 221the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 222small and misleading number. 223