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.Dd April 26, 2013 29.Dt SYSCONF 3 30.Os 31.Sh NAME 32.Nm sysconf 33.Nd get configurable system variables 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In 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.In unistd.h . 55Shell programmers who need access to these parameters should use the 56.Xr getconf 1 57utility. 58.Pp 59The available values are as follows: 60.Bl -tag -width 6n 61.It Li _SC_ARG_MAX 62The maximum bytes of argument to 63.Xr execve 2 . 64.It Li _SC_CHILD_MAX 65The maximum number of simultaneous processes per user id. 66.It Li _SC_CLK_TCK 67The frequency of the statistics clock in ticks per second. 68.It Li _SC_IOV_MAX 69The maximum number of elements in the I/O vector used by 70.Xr readv 2 , 71.Xr writev 2 , 72.Xr recvmsg 2 , 73and 74.Xr sendmsg 2 . 75.It Li _SC_NGROUPS_MAX 76The maximum number of supplemental groups. 77.It Li _SC_NPROCESSORS_CONF 78The number of processors configured. 79.It Li _SC_NPROCESSORS_ONLN 80The number of processors currently online. 81.It Li _SC_OPEN_MAX 82One more than the maximum value the system may assign to a new file descriptor. 83.It Li _SC_PAGESIZE 84The size of a system page in bytes. 85.It Li _SC_PAGE_SIZE 86Equivalent to 87.Li _SC_PAGESIZE . 88.It Li _SC_STREAM_MAX 89The minimum maximum number of streams that a process may have open 90at any one time. 91.It Li _SC_TZNAME_MAX 92The minimum maximum number of types supported for the name of a 93timezone. 94.It Li _SC_JOB_CONTROL 95Return 1 if job control is available on this system, otherwise \-1. 96.It Li _SC_SAVED_IDS 97Returns 1 if saved set-group and saved set-user ID is available, 98otherwise \-1. 99.It Li _SC_VERSION 100The version of 101.St -p1003.1 102with which the system 103attempts to comply. 104.It Li _SC_BC_BASE_MAX 105The maximum ibase/obase values in the 106.Xr bc 1 107utility. 108.It Li _SC_BC_DIM_MAX 109The maximum array size in the 110.Xr bc 1 111utility. 112.It Li _SC_BC_SCALE_MAX 113The maximum scale value in the 114.Xr bc 1 115utility. 116.It Li _SC_BC_STRING_MAX 117The maximum string length in the 118.Xr bc 1 119utility. 120.It Li _SC_COLL_WEIGHTS_MAX 121The maximum number of weights that can be assigned to any entry of 122the LC_COLLATE order keyword in the locale definition file. 123.It Li _SC_EXPR_NEST_MAX 124The maximum number of expressions that can be nested within 125parenthesis by the 126.Xr expr 1 127utility. 128.It Li _SC_LINE_MAX 129The maximum length in bytes of a text-processing utility's input 130line. 131.It Li _SC_RE_DUP_MAX 132The maximum number of repeated occurrences of a regular expression 133permitted when using interval notation. 134.It Li _SC_2_VERSION 135The version of 136.St -p1003.2 137with which the system attempts to comply. 138.It Li _SC_2_C_BIND 139Return 1 if the system's C-language development facilities support the 140C-Language Bindings Option, otherwise \-1. 141.It Li _SC_2_C_DEV 142Return 1 if the system supports the C-Language Development Utilities Option, 143otherwise \-1. 144.It Li _SC_2_CHAR_TERM 145Return 1 if the system supports at least one terminal type capable of 146all operations described in 147.St -p1003.2 , 148otherwise \-1. 149.It Li _SC_2_FORT_DEV 150Return 1 if the system supports the FORTRAN Development Utilities Option, 151otherwise \-1. 152.It Li _SC_2_FORT_RUN 153Return 1 if the system supports the FORTRAN Runtime Utilities Option, 154otherwise \-1. 155.It Li _SC_2_LOCALEDEF 156Return 1 if the system supports the creation of locales, otherwise \-1. 157.It Li _SC_2_SW_DEV 158Return 1 if the system supports the Software Development Utilities Option, 159otherwise \-1. 160.It Li _SC_2_UPE 161Return 1 if the system supports the User Portability Utilities Option, 162otherwise \-1. 163.It Li _SC_AIO_LISTIO_MAX 164Maximum number of I/O operations in a single list I/O call supported. 165.It Li _SC_AIO_MAX 166Maximum number of outstanding asynchronous I/O operations supported. 167.It Li _SC_AIO_PRIO_DELTA_MAX 168The maximum amount by which a process can decrease its asynchronous I/O 169priority level from its own scheduling priority. 170.It Li _SC_DELAYTIMER_MAX 171Maximum number of timer expiration overruns. 172.It Li _SC_MQ_OPEN_MAX 173The maximum number of open message queue descriptors a process may hold. 174.It Li _SC_RTSIG_MAX 175Maximum number of realtime signals reserved for application use. 176.It Li _SC_SEM_NSEMS_MAX 177Maximum number of semaphores that a process may have. 178.It Li _SC_SEM_VALUE_MAX 179The maximum value a semaphore may have. 180.It Li _SC_SIGQUEUE_MAX 181Maximum number of queued signals that a process may send and have pending at 182the receiver(s) at any time. 183.It Li _SC_TIMER_MAX 184Maximum number of timers per process supported. 185.It Li _SC_GETGR_R_SIZE_MAX 186Suggested initial value for the size of the group entry buffer. 187.It Li _SC_GETPW_R_SIZE_MAX 188Suggested initial value for the size of the password entry buffer. 189.It Li _SC_HOST_NAME_MAX 190Maximum length of a host name (not including the terminating null) as 191returned from the 192.Fn gethostname 193function. 194.It Li _SC_LOGIN_NAME_MAX 195Maximum length of a login name. 196.It Li _SC_THREAD_STACK_MIN 197Minimum size in bytes of thread stack storage. 198.It Li _SC_THREAD_THREADS_MAX 199Maximum number of threads that can be created per process. 200.It Li _SC_TTY_NAME_MAX 201Maximum length of terminal device name. 202.It Li _SC_SYMLOOP_MAX 203Maximum number of symbolic links that can be reliably traversed in the 204resolution of a pathname in the absence of a loop. 205.It Li _SC_ATEXIT_MAX 206Maximum number of functions that may be registered with 207.Fn atexit . 208.It Li _SC_XOPEN_VERSION 209An integer value greater than or equal to 4, 210indicating the version of the X/Open Portability Guide to which this 211system conforms. 212.It Li _SC_XOPEN_XCU_VERSION 213An integer value indicating the version of the XCU Specification to which 214this system conforms. 215.El 216.Pp 217These values also exist, but may not be standard: 218.Bl -tag -width 6n 219.It Li _SC_CPUSET_SIZE 220Size of the kernel cpuset. 221.It Li _SC_PHYS_PAGES 222The number of pages of physical memory. 223Note that it is possible that the product of this value and the value of 224.Li _SC_PAGESIZE 225will overflow a 226.Vt long 227in some configurations on a 32bit machine. 228.El 229.Sh RETURN VALUES 230If the call to 231.Fn sysconf 232is not successful, \-1 is returned and 233.Va errno 234is set appropriately. 235Otherwise, if the variable is associated with functionality that is not 236supported, \-1 is returned and 237.Va errno 238is not modified. 239Otherwise, the current variable value is returned. 240.Sh ERRORS 241The 242.Fn sysconf 243function may fail and set 244.Va errno 245for any of the errors specified for the library function 246.Xr sysctl 3 . 247In addition, the following error may be reported: 248.Bl -tag -width Er 249.It Bq Er EINVAL 250The value of the 251.Fa name 252argument is invalid. 253.El 254.Sh SEE ALSO 255.Xr getconf 1 , 256.Xr pathconf 2 , 257.Xr confstr 3 , 258.Xr sysctl 3 259.Sh STANDARDS 260Except for the fact that values returned by 261.Fn sysconf 262may change over the lifetime of the calling process, 263this function conforms to 264.St -p1003.1-88 . 265.Sh HISTORY 266The 267.Fn sysconf 268function first appeared in 269.Bx 4.4 . 270.Sh BUGS 271The value for _SC_STREAM_MAX is a minimum maximum, and required to be 272the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 273small and misleading number. 274