1.\" $OpenBSD: sysconf.3,v 1.30 2012/03/06 13:57:16 jmc 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: March 6 2012 $ 31.Dt SYSCONF 3 32.Os 33.Sh NAME 34.Nm sysconf 35.Nd get configurable system variables 36.Sh SYNOPSIS 37.Fd #include <unistd.h> 38.Ft long 39.Fn sysconf "int name" 40.Sh DESCRIPTION 41This interface is defined by 42.St -p1003.1-88 . 43A far more complete interface is available using 44.Xr sysctl 3 . 45.Pp 46The 47.Fn sysconf 48function provides a method for applications to determine the current 49value of a configurable system limit or option variable. 50The 51.Fa name 52argument specifies the system variable to be queried. 53Symbolic constants for each name value are found in the include file 54.Aq Pa unistd.h . 55.Pp 56The available values are as follows: 57.Bl -tag -width "123456" 58.It Li _SC_ARG_MAX 59The maximum bytes of arguments to 60.Xr exec 3 61(including the environment). 62.It Li _SC_CHILD_MAX 63The maximum number of simultaneous processes per user ID. 64.It Li _SC_CLK_TCK 65The number of clock ticks per second. 66.It Li _SC_NGROUPS_MAX 67The maximum number of supplemental groups. 68.It Li _SC_OPEN_MAX 69The maximum number of open files per user ID. 70.It Li _SC_STREAM_MAX 71The minimum maximum number of streams that a process may have open 72at any one time. 73.It Li _SC_TZNAME_MAX 74The minimum maximum number of types supported for the name of a 75time zone. 76.It Li _SC_JOB_CONTROL 77Returns 1 if job control is available on this system, otherwise \-1. 78.It Li _SC_SAVED_IDS 79Returns 1 if saved set-group-ID and saved set-user-ID is available, 80otherwise \-1. 81.It Li _SC_VERSION 82The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 83attempts to comply. 84.It Li _SC_BC_BASE_MAX 85The maximum ibase/obase values in the 86.Xr bc 1 87utility. 88.It Li _SC_BC_DIM_MAX 89The maximum array size in the 90.Xr bc 1 91utility. 92.It Li _SC_BC_SCALE_MAX 93The maximum scale value in the 94.Xr bc 1 95utility. 96.It Li _SC_BC_STRING_MAX 97The maximum string length in the 98.Xr bc 1 99utility. 100.It Li _SC_COLL_WEIGHTS_MAX 101The maximum number of weights that can be assigned to any entry of 102the LC_COLLATE order keyword in the locale definition file. 103.It Li _SC_EXPR_NEST_MAX 104The maximum number of expressions that can be nested within 105parentheses by the 106.Xr expr 1 107utility. 108.It Li _SC_LINE_MAX 109The maximum length in bytes of a text-processing utility's input 110line. 111.It Li _SC_RE_DUP_MAX 112The maximum number of repeated occurrences of a regular expression 113permitted when using interval notation. 114.It Li _SC_2_VERSION 115The version of POSIX 1003.2 with which the system attempts to comply. 116.It Li _SC_2_C_BIND 117Return 1 if the system's C-language development facilities support the 118C-Language Bindings Option, otherwise \-1. 119.It Li _SC_2_C_DEV 120Return 1 if the system supports the C-Language Development Utilities Option, 121otherwise \-1. 122.It Li _SC_2_CHAR_TERM 123Return 1 if the system supports at least one terminal type capable of 124all operations described in POSIX 1003.2, otherwise \-1. 125.It Li _SC_2_FORT_DEV 126Return 1 if the system supports the FORTRAN Development Utilities Option, 127otherwise \-1. 128.It Li _SC_2_FORT_RUN 129Return 1 if the system supports the FORTRAN Runtime Utilities Option, 130otherwise \-1. 131.It Li _SC_2_LOCALEDEF 132Return 1 if the system supports the creation of locales, otherwise \-1. 133.It Li _SC_2_SW_DEV 134Return 1 if the system supports the Software Development Utilities Option, 135otherwise \-1. 136.It Li _SC_2_UPE 137Return 1 if the system supports the User Portability Utilities Option, 138otherwise \-1. 139.It Li _SC_PAGESIZE 140The size of a system page in bytes. 141.It Li _SC_FSYNC 142Return 1 if the system supports the File Synchronisation Option, otherwise \-1. 143.It Li _SC_XOPEN_SHM 144Return 1 if the system supports the Shared Memory Option, otherwise \-1. 145.It Li _SC_SEM_NSEMS_MAX 146The maximum number of semaphores in the system or \-1 if the system 147does not support the Semaphores Option. 148.It Li _SC_SEM_VALUE_MAX 149The maximum value a semaphore may have or \-1 if the system 150does not support the Semaphores Option. 151.It Li _SC_PHYS_PAGES 152The number of pages of physical memory. 153.It Li _SC_AVPHYS_PAGES 154The number of pages of physical memory not currently in use by the system. 155.It Li _SC_GETGR_R_SIZE_MAX 156The maximum size of the data buffer for the 157.Fn getgrgid_r 158and 159.Fn getgrnam_r 160functions. 161.It Li _SC_GETPW_R_SIZE_MAX 162The maximum size of the data buffer for the 163.Fn getpwuid_r 164and 165.Fn getpwnam_r 166functions. 167.It Li _SC_LOGIN_NAME_MAX 168The maximum length of a login name. 169.It Li _SC_THREAD_SAFE_FUNCTIONS 170The level of support for thread-safe (re-entrant) functions. 171.It Li _SC_NPROCESSORS_CONF 172The number of processors configured. 173.It Li _SC_NPROCESSORS_ONLN 174The number of processors online (capable of running processes). 175.It Li _SC_HOST_NAME_MAX 176The maximum size of a hostname, not counting NULL. 177.It Li _SC_MONOTONIC_CLOCK 178Return the POSIX version of the implementation of the Monotonic Clock 179option that this system conforms to, or \-1 if unavailable. 180.El 181.Sh RETURN VALUES 182If the call to 183.Fn sysconf 184is not successful, \-1 is returned and 185.Va errno 186is set appropriately. 187Otherwise, if the variable is associated with functionality that is not 188supported, \-1 is returned and 189.Va errno 190is not modified. 191Otherwise, the current variable value is returned. 192.Sh ERRORS 193The 194.Fn sysconf 195function may fail and set 196.Va errno 197for any of the errors specified for the library function 198.Xr sysctl 3 . 199In addition, the following error may be reported: 200.Bl -tag -width Er 201.It Bq Er EINVAL 202The value of the 203.Fa name 204argument is invalid. 205.El 206.Sh SEE ALSO 207.Xr pathconf 2 , 208.Xr sysctl 3 209.Sh STANDARDS 210The 211.Fn sysconf 212function conforms to 213.St -p1003.1-88 . 214The constants 215.Li _SC_NPROCESSORS_CONF 216and 217.Li _SC_NPROCESSORS_ONLN 218are not part of the standard, but are provided by many systems. 219.Sh HISTORY 220The 221.Fn sysconf 222function first appeared in 223.Bx 4.4 . 224.Sh BUGS 225The value for _SC_STREAM_MAX is a minimum maximum, and required to be 226the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 227small and misleading number. 228