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.\" 30.Dd April 26, 2013 31.Dt SYSCONF 3 32.Os 33.Sh NAME 34.Nm sysconf 35.Nd get configurable system variables 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In unistd.h 40.Ft long 41.Fn sysconf "int name" 42.Sh DESCRIPTION 43This interface is defined by 44.St -p1003.1-88 . 45A far more complete interface is available using 46.Xr sysctl 3 . 47.Pp 48The 49.Fn sysconf 50function provides a method for applications to determine the current 51value of a configurable system limit or option variable. 52The 53.Fa name 54argument specifies the system variable to be queried. 55Symbolic constants for each name value are found in the include file 56.In unistd.h . 57Shell programmers who need access to these parameters should use the 58.Xr getconf 1 59utility. 60.Pp 61The available values are as follows: 62.Bl -tag -width 6n 63.It Li _SC_ARG_MAX 64The maximum bytes of argument to 65.Xr execve 2 . 66.It Li _SC_CHILD_MAX 67The maximum number of simultaneous processes per user id. 68.It Li _SC_CLK_TCK 69The frequency of the statistics clock in ticks per second. 70.It Li _SC_IOV_MAX 71The maximum number of elements in the I/O vector used by 72.Xr readv 2 , 73.Xr writev 2 , 74.Xr recvmsg 2 , 75and 76.Xr sendmsg 2 . 77.It Li _SC_NGROUPS_MAX 78The maximum number of supplemental groups. 79.It Li _SC_NPROCESSORS_CONF 80The number of processors configured. 81.It Li _SC_NPROCESSORS_ONLN 82The number of processors currently online. 83.It Li _SC_OPEN_MAX 84One more than the maximum value the system may assign to a new file descriptor. 85.It Li _SC_PAGESIZE 86The size of a system page in bytes. 87.It Li _SC_PAGE_SIZE 88Equivalent to 89.Li _SC_PAGESIZE . 90.It Li _SC_STREAM_MAX 91The minimum maximum number of streams that a process may have open 92at any one time. 93.It Li _SC_TZNAME_MAX 94The minimum maximum number of types supported for the name of a 95timezone. 96.It Li _SC_JOB_CONTROL 97Return 1 if job control is available on this system, otherwise \-1. 98.It Li _SC_SAVED_IDS 99Returns 1 if saved set-group and saved set-user ID is available, 100otherwise \-1. 101.It Li _SC_VERSION 102The version of 103.St -p1003.1 104with which the system 105attempts to comply. 106.It Li _SC_BC_BASE_MAX 107The maximum ibase/obase values in the 108.Xr bc 1 109utility. 110.It Li _SC_BC_DIM_MAX 111The maximum array size in the 112.Xr bc 1 113utility. 114.It Li _SC_BC_SCALE_MAX 115The maximum scale value in the 116.Xr bc 1 117utility. 118.It Li _SC_BC_STRING_MAX 119The maximum string length in the 120.Xr bc 1 121utility. 122.It Li _SC_COLL_WEIGHTS_MAX 123The maximum number of weights that can be assigned to any entry of 124the LC_COLLATE order keyword in the locale definition file. 125.It Li _SC_EXPR_NEST_MAX 126The maximum number of expressions that can be nested within 127parenthesis by the 128.Xr expr 1 129utility. 130.It Li _SC_LINE_MAX 131The maximum length in bytes of a text-processing utility's input 132line. 133.It Li _SC_RE_DUP_MAX 134The maximum number of repeated occurrences of a regular expression 135permitted when using interval notation. 136.It Li _SC_2_VERSION 137The version of 138.St -p1003.2 139with which the system attempts to comply. 140.It Li _SC_2_C_BIND 141Return 1 if the system's C-language development facilities support the 142C-Language Bindings Option, otherwise \-1. 143.It Li _SC_2_C_DEV 144Return 1 if the system supports the C-Language Development Utilities Option, 145otherwise \-1. 146.It Li _SC_2_CHAR_TERM 147Return 1 if the system supports at least one terminal type capable of 148all operations described in 149.St -p1003.2 , 150otherwise \-1. 151.It Li _SC_2_FORT_DEV 152Return 1 if the system supports the FORTRAN Development Utilities Option, 153otherwise \-1. 154.It Li _SC_2_FORT_RUN 155Return 1 if the system supports the FORTRAN Runtime Utilities Option, 156otherwise \-1. 157.It Li _SC_2_LOCALEDEF 158Return 1 if the system supports the creation of locales, otherwise \-1. 159.It Li _SC_2_SW_DEV 160Return 1 if the system supports the Software Development Utilities Option, 161otherwise \-1. 162.It Li _SC_2_UPE 163Return 1 if the system supports the User Portability Utilities Option, 164otherwise \-1. 165.It Li _SC_AIO_LISTIO_MAX 166Maximum number of I/O operations in a single list I/O call supported. 167.It Li _SC_AIO_MAX 168Maximum number of outstanding asynchronous I/O operations supported. 169.It Li _SC_AIO_PRIO_DELTA_MAX 170The maximum amount by which a process can decrease its asynchronous I/O 171priority level from its own scheduling priority. 172.It Li _SC_DELAYTIMER_MAX 173Maximum number of timer expiration overruns. 174.It Li _SC_MQ_OPEN_MAX 175The maximum number of open message queue descriptors a process may hold. 176.It Li _SC_RTSIG_MAX 177Maximum number of realtime signals reserved for application use. 178.It Li _SC_SEM_NSEMS_MAX 179Maximum number of semaphores that a process may have. 180.It Li _SC_SEM_VALUE_MAX 181The maximum value a semaphore may have. 182.It Li _SC_SIGQUEUE_MAX 183Maximum number of queued signals that a process may send and have pending at 184the receiver(s) at any time. 185.It Li _SC_TIMER_MAX 186Maximum number of timers per process supported. 187.It Li _SC_GETGR_R_SIZE_MAX 188Suggested initial value for the size of the group entry buffer. 189.It Li _SC_GETPW_R_SIZE_MAX 190Suggested initial value for the size of the password entry buffer. 191.It Li _SC_HOST_NAME_MAX 192Maximum length of a host name (not including the terminating null) as 193returned from the 194.Fn gethostname 195function. 196.It Li _SC_LOGIN_NAME_MAX 197Maximum length of a login name. 198.It Li _SC_THREAD_STACK_MIN 199Minimum size in bytes of thread stack storage. 200.It Li _SC_THREAD_THREADS_MAX 201Maximum number of threads that can be created per process. 202.It Li _SC_TTY_NAME_MAX 203Maximum length of terminal device name. 204.It Li _SC_SYMLOOP_MAX 205Maximum number of symbolic links that can be reliably traversed in the 206resolution of a pathname in the absence of a loop. 207.It Li _SC_ATEXIT_MAX 208Maximum number of functions that may be registered with 209.Fn atexit . 210.It Li _SC_XOPEN_VERSION 211An integer value greater than or equal to 4, 212indicating the version of the X/Open Portability Guide to which this 213system conforms. 214.It Li _SC_XOPEN_XCU_VERSION 215An integer value indicating the version of the XCU Specification to which 216this system conforms. 217.El 218.Pp 219These values also exist, but may not be standard: 220.Bl -tag -width 6n 221.It Li _SC_CPUSET_SIZE 222Size of the kernel cpuset. 223.It Li _SC_PHYS_PAGES 224The number of pages of physical memory. 225Note that it is possible that the product of this value and the value of 226.Li _SC_PAGESIZE 227will overflow a 228.Vt long 229in some configurations on a 32bit machine. 230.El 231.Sh RETURN VALUES 232If the call to 233.Fn sysconf 234is not successful, \-1 is returned and 235.Va errno 236is set appropriately. 237Otherwise, if the variable is associated with functionality that is not 238supported, \-1 is returned and 239.Va errno 240is not modified. 241Otherwise, the current variable value is returned. 242.Sh ERRORS 243The 244.Fn sysconf 245function may fail and set 246.Va errno 247for any of the errors specified for the library function 248.Xr sysctl 3 . 249In addition, the following error may be reported: 250.Bl -tag -width Er 251.It Bq Er EINVAL 252The value of the 253.Fa name 254argument is invalid. 255.El 256.Sh SEE ALSO 257.Xr getconf 1 , 258.Xr pathconf 2 , 259.Xr confstr 3 , 260.Xr sysctl 3 261.Sh STANDARDS 262Except for the fact that values returned by 263.Fn sysconf 264may change over the lifetime of the calling process, 265this function conforms to 266.St -p1003.1-88 . 267.Sh HISTORY 268The 269.Fn sysconf 270function first appeared in 271.Bx 4.4 . 272.Sh BUGS 273The value for _SC_STREAM_MAX is a minimum maximum, and required to be 274the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 275small and misleading number. 276