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 June 10, 2021 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_HOST_NAME_MAX 93Maximum length of a host name (not including the terminating null) as 94returned from the 95.Xr gethostname 3 , 96function. 97.It Dv _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 Dv _SC_JOB_CONTROL 105Return 1 if job control is available on this system, otherwise \-1. 106.It Dv _SC_LINE_MAX 107The maximum length in bytes of a text-processing utility's input 108line. 109.It Dv _SC_MESSAGE_PASSING 110Whether Message Passing option is supported. 111.It Dv _SC_MQ_OPEN_MAX 112The maximum number of open message queue descriptors per process. 113.It Dv _SC_MQ_PRIO_MAX 114The maximum number of message priorities supported by the implementation. 115.It Dv _SC_NGROUPS_MAX 116The maximum number of supplemental groups. 117.It Dv _SC_OPEN_MAX 118The maximum number of open files per user id. 119.It Dv _SC_PAGESIZE 120The size of a system page in bytes. 121.It Dv _SC_PAGE_SIZE 122Equivalent to 123.Dv _SC_PAGESIZE . 124.It Dv _SC_RE_DUP_MAX 125The maximum number of repeated occurrences of a regular expression 126permitted when using interval notation. 127.It Dv _SC_REGEXP 128Return 1 if the system supports regular expression handling. 129.It Dv _SC_SAVED_IDS 130Return 1 if saved set-group and saved set-user ID is available, 131otherwise \-1. 132.It Dv _SC_SHELL 133Return 1 if the system supports the 134.Tn POSIX 135shell. 136.It Dv _SC_STREAM_MAX 137The minimum maximum number of streams that a process may have open 138at any one time. 139.It Dv _SC_TZNAME_MAX 140The minimum maximum number of types supported for the name of a 141timezone. 142.It Dv _SC_VERSION 143The version of 144.St -p1003.1 145with which the system 146attempts to comply. 147.It Dv _SC_XOPEN_SHM 148Return 1 if the system supports the 149.St -xpg4.2 150Shared Memory Feature 151for both compilation and execution, or 0 if only compilation support is 152guaranteed. 153.It Dv _SC_2_C_BIND 154Return 1 if the system's C-language development facilities support the 155C-Language Bindings Option, otherwise \-1. 156.It Dv _SC_2_C_DEV 157Return 1 if the system supports the C-Language Development Utilities Option, 158otherwise \-1. 159.It Dv _SC_2_CHAR_TERM 160Return 1 if the system supports at least one terminal type capable of 161all operations described in 162.St -p1003.2 , 163otherwise \-1. 164.It Dv _SC_2_FORT_DEV 165Return 1 if the system supports the FORTRAN Development Utilities Option, 166otherwise \-1. 167.It Dv _SC_2_FORT_RUN 168Return 1 if the system supports the FORTRAN Runtime Utilities Option, 169otherwise \-1. 170.It Dv _SC_2_LOCALEDEF 171Return 1 if the system supports the creation of locales, otherwise \-1. 172.It Dv _SC_2_SW_DEV 173Return 1 if the system supports the Software Development Utilities Option, 174otherwise \-1. 175.It Dv _SC_2_UPE 176Return 1 if the system supports the User Portability Utilities Option, 177otherwise \-1. 178.It Dv _SC_2_VERSION 179The version of 180.St -p1003.2 181with which the system attempts to comply. 182.El 183.Pp 184These values also exist, but may not be standard: 185.Bl -tag -width 6n 186.It Dv _SC_LEVEL1_DCACHE_LINESIZE 187Returns the L1 cache line size. 188.It Dv _SC_NPROCESSORS_CONF 189The number of processors configured. 190.It Dv _SC_NPROCESSORS_ONLN 191The number of processors online. 192.It Dv _SC_PHYS_PAGES 193The number of pages of physical memory. 194.El 195.Sh RETURN VALUES 196If the call to 197.Fn sysconf 198is not successful, \-1 is returned and 199.Va errno 200is set appropriately. 201Otherwise, if the variable is associated with functionality that is not 202supported, \-1 is returned and 203.Va errno 204is not modified. 205Otherwise, the current variable value is returned. 206.Sh ERRORS 207The 208.Fn sysconf 209function may fail and set 210.Va errno 211for any of the errors specified for the library function 212.Xr sysctl 3 . 213In addition, the following error may be reported: 214.Bl -tag -width Er 215.It Bq Er EINVAL 216The value of the 217.Fa name 218argument is invalid. 219.El 220.Sh SEE ALSO 221.Xr getconf 1 , 222.Xr pathconf 2 , 223.Xr confstr 3 , 224.Xr sysctl 3 225.Sh STANDARDS 226Except for the fact that values returned by 227.Fn sysconf 228may change over the lifetime of the calling process, 229this function conforms to 230.St -p1003.1-88 . 231.Pp 232.Dv _SC_NPROCESSORS_CONF 233and 234.Dv _SC_NPROCESSORS_ONLN 235are nonstandard, but implemented in many systems. 236.Sh HISTORY 237The 238.Fn sysconf 239function first appeared in 240.Bx 4.4 . 241.Sh BUGS 242The value for 243.Dv _SC_STREAM_MAX 244is a minimum maximum, and required to be the same as ANSI C's 245.Dv FOPEN_MAX , 246so the returned value is a ridiculously small and misleading number. 247