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.\" $FreeBSD$ 30.\" 31.Dd April 26, 2013 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 . 58Shell programmers who need access to these parameters should use the 59.Xr getconf 1 60utility. 61.Pp 62The available values are as follows: 63.Bl -tag -width 6n 64.It Li _SC_ARG_MAX 65The maximum bytes of argument to 66.Xr execve 2 . 67.It Li _SC_CHILD_MAX 68The maximum number of simultaneous processes per user id. 69.It Li _SC_CLK_TCK 70The frequency of the statistics clock in ticks per second. 71.It Li _SC_IOV_MAX 72The maximum number of elements in the I/O vector used by 73.Xr readv 2 , 74.Xr writev 2 , 75.Xr recvmsg 2 , 76and 77.Xr sendmsg 2 . 78.It Li _SC_NGROUPS_MAX 79The maximum number of supplemental groups. 80.It Li _SC_NPROCESSORS_CONF 81The number of processors configured. 82.It Li _SC_NPROCESSORS_ONLN 83The number of processors currently online. 84.It Li _SC_OPEN_MAX 85One more than the maximum value the system may assign to a new file descriptor. 86.It Li _SC_PAGESIZE 87The size of a system page in bytes. 88.It Li _SC_PAGE_SIZE 89Equivalent to 90.Li _SC_PAGESIZE . 91.It Li _SC_STREAM_MAX 92The minimum maximum number of streams that a process may have open 93at any one time. 94.It Li _SC_TZNAME_MAX 95The minimum maximum number of types supported for the name of a 96timezone. 97.It Li _SC_JOB_CONTROL 98Return 1 if job control is available on this system, otherwise \-1. 99.It Li _SC_SAVED_IDS 100Returns 1 if saved set-group and saved set-user ID is available, 101otherwise \-1. 102.It Li _SC_VERSION 103The version of 104.St -p1003.1 105with which the system 106attempts to comply. 107.It Li _SC_BC_BASE_MAX 108The maximum ibase/obase values in the 109.Xr bc 1 110utility. 111.It Li _SC_BC_DIM_MAX 112The maximum array size in the 113.Xr bc 1 114utility. 115.It Li _SC_BC_SCALE_MAX 116The maximum scale value in the 117.Xr bc 1 118utility. 119.It Li _SC_BC_STRING_MAX 120The maximum string length in the 121.Xr bc 1 122utility. 123.It Li _SC_COLL_WEIGHTS_MAX 124The maximum number of weights that can be assigned to any entry of 125the LC_COLLATE order keyword in the locale definition file. 126.It Li _SC_EXPR_NEST_MAX 127The maximum number of expressions that can be nested within 128parenthesis by the 129.Xr expr 1 130utility. 131.It Li _SC_LINE_MAX 132The maximum length in bytes of a text-processing utility's input 133line. 134.It Li _SC_RE_DUP_MAX 135The maximum number of repeated occurrences of a regular expression 136permitted when using interval notation. 137.It Li _SC_2_VERSION 138The version of 139.St -p1003.2 140with which the system attempts to comply. 141.It Li _SC_2_C_BIND 142Return 1 if the system's C-language development facilities support the 143C-Language Bindings Option, otherwise \-1. 144.It Li _SC_2_C_DEV 145Return 1 if the system supports the C-Language Development Utilities Option, 146otherwise \-1. 147.It Li _SC_2_CHAR_TERM 148Return 1 if the system supports at least one terminal type capable of 149all operations described in 150.St -p1003.2 , 151otherwise \-1. 152.It Li _SC_2_FORT_DEV 153Return 1 if the system supports the FORTRAN Development Utilities Option, 154otherwise \-1. 155.It Li _SC_2_FORT_RUN 156Return 1 if the system supports the FORTRAN Runtime Utilities Option, 157otherwise \-1. 158.It Li _SC_2_LOCALEDEF 159Return 1 if the system supports the creation of locales, otherwise \-1. 160.It Li _SC_2_SW_DEV 161Return 1 if the system supports the Software Development Utilities Option, 162otherwise \-1. 163.It Li _SC_2_UPE 164Return 1 if the system supports the User Portability Utilities Option, 165otherwise \-1. 166.It Li _SC_AIO_LISTIO_MAX 167Maximum number of I/O operations in a single list I/O call supported. 168.It Li _SC_AIO_MAX 169Maximum number of outstanding asynchronous I/O operations supported. 170.It Li _SC_AIO_PRIO_DELTA_MAX 171The maximum amount by which a process can decrease its asynchronous I/O 172priority level from its own scheduling priority. 173.It Li _SC_DELAYTIMER_MAX 174Maximum number of timer expiration overruns. 175.It Li _SC_MQ_OPEN_MAX 176The maximum number of open message queue descriptors a process may hold. 177.It Li _SC_RTSIG_MAX 178Maximum number of realtime signals reserved for application use. 179.It Li _SC_SEM_NSEMS_MAX 180Maximum number of semaphores that a process may have. 181.It Li _SC_SEM_VALUE_MAX 182The maximum value a semaphore may have. 183.It Li _SC_SIGQUEUE_MAX 184Maximum number of queued signals that a process may send and have pending at 185the receiver(s) at any time. 186.It Li _SC_TIMER_MAX 187Maximum number of timers per process supported. 188.It Li _SC_GETGR_R_SIZE_MAX 189Suggested initial value for the size of the group entry buffer. 190.It Li _SC_GETPW_R_SIZE_MAX 191Suggested initial value for the size of the password entry buffer. 192.It Li _SC_HOST_NAME_MAX 193Maximum length of a host name (not including the terminating null) as 194returned from the 195.Fn gethostname 196function. 197.It Li _SC_LOGIN_NAME_MAX 198Maximum length of a login name. 199.It Li _SC_THREAD_STACK_MIN 200Minimum size in bytes of thread stack storage. 201.It Li _SC_THREAD_THREADS_MAX 202Maximum number of threads that can be created per process. 203.It Li _SC_TTY_NAME_MAX 204Maximum length of terminal device name. 205.It Li _SC_SYMLOOP_MAX 206Maximum number of symbolic links that can be reliably traversed in the 207resolution of a pathname in the absence of a loop. 208.It Li _SC_ATEXIT_MAX 209Maximum number of functions that may be registered with 210.Fn atexit . 211.It Li _SC_XOPEN_VERSION 212An integer value greater than or equal to 4, 213indicating the version of the X/Open Portability Guide to which this 214system conforms. 215.It Li _SC_XOPEN_XCU_VERSION 216An integer value indicating the version of the XCU Specification to which 217this system conforms. 218.El 219.Pp 220These values also exist, but may not be standard: 221.Bl -tag -width 6n 222.It Li _SC_CPUSET_SIZE 223Size of the kernel cpuset. 224.It Li _SC_PHYS_PAGES 225The number of pages of physical memory. 226Note that it is possible that the product of this value and the value of 227.Li _SC_PAGESIZE 228will overflow a 229.Vt long 230in some configurations on a 32bit machine. 231.El 232.Sh RETURN VALUES 233If the call to 234.Fn sysconf 235is not successful, \-1 is returned and 236.Va errno 237is set appropriately. 238Otherwise, if the variable is associated with functionality that is not 239supported, \-1 is returned and 240.Va errno 241is not modified. 242Otherwise, the current variable value is returned. 243.Sh ERRORS 244The 245.Fn sysconf 246function may fail and set 247.Va errno 248for any of the errors specified for the library function 249.Xr sysctl 3 . 250In addition, the following error may be reported: 251.Bl -tag -width Er 252.It Bq Er EINVAL 253The value of the 254.Fa name 255argument is invalid. 256.El 257.Sh SEE ALSO 258.Xr getconf 1 , 259.Xr pathconf 2 , 260.Xr confstr 3 , 261.Xr sysctl 3 262.Sh STANDARDS 263Except for the fact that values returned by 264.Fn sysconf 265may change over the lifetime of the calling process, 266this function conforms to 267.St -p1003.1-88 . 268.Sh HISTORY 269The 270.Fn sysconf 271function first appeared in 272.Bx 4.4 . 273.Sh BUGS 274The value for _SC_STREAM_MAX is a minimum maximum, and required to be 275the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 276small and misleading number. 277