1.\" $NetBSD: sysconf.3,v 1.34 2008/08/06 17:17:04 matt 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.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 31.\" 32.Dd August 14, 2006 33.Dt SYSCONF 3 34.Os 35.Sh NAME 36.Nm sysconf 37.Nd get configurable system variables 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft long 43.Fn sysconf "int name" 44.Sh DESCRIPTION 45This interface is defined by 46.St -p1003.1-88 . 47A far more complete interface is available using 48.Xr sysctl 3 . 49.Pp 50The 51.Fn sysconf 52function provides a method for applications to determine the current 53value of a configurable system limit or option variable. 54The 55.Fa name 56argument specifies the system variable to be queried. 57Symbolic constants for each name value are found in the include file 58.Aq Pa unistd.h . 59.Pp 60The available values are as follows: 61.Pp 62.Bl -tag -width "123456" 63.Pp 64.It Li _SC_ARG_MAX 65The maximum bytes of argument to 66.Xr execve 2 . 67.It Li _SC_ATEXIT_MAX 68The maxmimum number of functions that may be registered with 69.Xr atexit 3 . 70.It Li _SC_BARRIERS 71The version of 72.St -p1003.1 73and its 74Barriers 75option to which the system attempts to conform, 76otherwise \-1. 77.It Li _SC_CLOCK_SELECTION 78Return the 79.Tn POSIX 80version the implementation of the Clock Selection Option 81on this system conforms to, 82or \-1 if unavailable. 83.It Li _SC_CHILD_MAX 84The maximum number of simultaneous processes per user id. 85.It Li _SC_CLK_TCK 86The number of clock ticks per second. 87.It Li _SC_FSYNC 88Return 1 if the File Synchronization Option is available on this system, 89otherwise \-1. 90.It Li _SC_HOST_NAME_MAX 91The maximum size of a hostname, including NULL. 92.It Li _SC_IOV_MAX 93The maximum number of 94.Va iovec 95structures that a process has available for use with 96.Xr preadv 2 , 97.Xr pwritev 2 , 98.Xr readv 2 , 99.Xr recvmsg 2 , 100.Xr sendmsg 2 101or 102.Xr writev 2 . 103.It Li _SC_JOB_CONTROL 104Return 1 if job control is available on this system, otherwise \-1. 105.It Li _SC_LOGIN_NAME_MAX 106Returns the size of the storage required for a login name, in bytes, 107including the terminating NUL. 108.It Li _SC_MAPPED_FILES 109Return 1 if the Memory Mapped Files Option is available on this system, 110otherwise \-1. 111.It Li _SC_MEMLOCK 112Return 1 if the Process Memory Locking Option is available on this system, 113otherwise \-1. 114.It Li _SC_MEMLOCK_RANGE 115Return 1 if the Range Memory Locking Option is available on this system, 116otherwise \-1. 117.It Li _SC_MEMORY_PROTECTION 118Return 1 if the Memory Protection Option is available on this system, 119otherwise \-1. 120.It Li _SC_MONOTONIC_CLOCK 121Return the 122.Tn POSIX 123version the implementation of the Monotonic Clock Option 124on this system conforms to, 125or \-1 if unavailable. 126.It Li _SC_NGROUPS_MAX 127The maximum number of supplemental groups. 128.It Li _SC_OPEN_MAX 129The maximum number of open files per process. 130.It Li _SC_PAGESIZE 131The size of a system page in bytes. 132.It Li _SC_PASS_MAX 133The maximum length of the password, not counting NULL. 134.It Li _SC_READER_WRITER_LOCKS 135The version of 136.St -p1003.1 137and its 138Read-Write Locks 139option to which the system attempts to conform, 140otherwise \-1. 141.It Li _SC_REGEXP 142Return 1 if 143.Tn POSIX 144regular expressions are available on this system, otherwise \-1. 145.It Li _SC_SEMAPHORES 146The version of 147.St -p1003.1 148and its 149Semaphores 150option to which the system attempts to conform, 151otherwise \-1. 152.Pp 153Availability of the 154Semaphores 155option depends on the 156.Li P1003_1B_SEMAPHORE 157kernel option. 158.It Li _SC_SHELL 159Return 1 if 160.Tn POSIX 161shell is available on this system, otherwise \-1. 162.It Li _SC_SPIN_LOCKS 163The version of 164.St -p1003.1 165and its 166Spin Locks 167option to which the system attempts to conform, 168otherwise \-1. 169.It Li _SC_STREAM_MAX 170The minimum maximum number of streams that a process may have open 171at any one time. 172.It Li _SC_SYMLOOP_MAX 173The maximum number of symbolic links that may be expanded in a path name. 174.It Li _SC_SYNCHRONIZED_IO 175Return 1 if the Synchronized I/O Option is available on this system, 176otherwise \-1. 177.It Li _SC_THREADS 178The version of 179.St -p1003.1 180and its 181Threads 182option to which the system attempts to conform, 183otherwise \-1. 184.It Li _SC_TIMERS 185The version of 186.St -p1003.1 187and its 188Timers 189option to which the system attempts to conform, 190otherwise \-1. 191.It Li _SC_TZNAME_MAX 192The minimum maximum number of types supported for the name of a 193timezone. 194.It Li _SC_SAVED_IDS 195Returns 1 if saved set-group and saved set-user ID is available, 196otherwise \-1. 197.It Li _SC_VERSION 198The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 199attempts to comply. 200.It Li _SC_XOPEN_SHM 201Return 1 if the 202.St -xpg4.2 203Shared Memory 204option is available on this system, 205otherwise \-1. 206.Pp 207Availability of the 208Shared Memory 209option depends on the 210.Li SYSVSHM 211kernel option. 212.It Li _SC_BC_BASE_MAX 213The maximum ibase/obase values in the 214.Xr bc 1 215utility. 216.It Li _SC_BC_DIM_MAX 217The maximum array size in the 218.Xr bc 1 219utility. 220.It Li _SC_BC_SCALE_MAX 221The maximum scale value in the 222.Xr bc 1 223utility. 224.It Li _SC_BC_STRING_MAX 225The maximum string length in the 226.Xr bc 1 227utility. 228.It Li _SC_COLL_WEIGHTS_MAX 229The maximum number of weights that can be assigned to any entry of 230the LC_COLLATE order keyword in the locale definition file. 231.It Li _SC_EXPR_NEST_MAX 232The maximum number of expressions that can be nested within 233parenthesis by the 234.Xr expr 1 235utility. 236.It Li _SC_LINE_MAX 237The maximum length in bytes of a text-processing utility's input 238line. 239.It Li _SC_RE_DUP_MAX 240The maximum number of repeated occurrences of a regular expression 241permitted when using interval notation. 242.It Li _SC_2_VERSION 243The version of POSIX 1003.2 with which the system attempts to comply. 244.It Li _SC_2_C_BIND 245Return 1 if the system's C-language development facilities support the 246C-Language Bindings Option, otherwise \-1. 247.It Li _SC_2_C_DEV 248Return 1 if the system supports the C-Language Development Utilities Option, 249otherwise \-1. 250.It Li _SC_2_CHAR_TERM 251Return 1 if the system supports at least one terminal type capable of 252all operations described in POSIX 1003.2, otherwise \-1. 253.It Li _SC_2_FORT_DEV 254Return 1 if the system supports the FORTRAN Development Utilities Option, 255otherwise \-1. 256.It Li _SC_2_FORT_RUN 257Return 1 if the system supports the FORTRAN Runtime Utilities Option, 258otherwise \-1. 259.It Li _SC_2_LOCALEDEF 260Return 1 if the system supports the creation of locales, otherwise \-1. 261.It Li _SC_2_SW_DEV 262Return 1 if the system supports the Software Development Utilities Option, 263otherwise \-1. 264.It Li _SC_2_UPE 265Return 1 if the system supports the User Portability Utilities Option, 266otherwise \-1. 267.It Li _SC_GETGR_R_SIZE_MAX 268The minimum size of the 269.Fa buffer 270passed to 271.Xr getgrgid_r 3 272and 273.Xr getgrnam_r 3 . 274.It Li _SC_GETPW_R_SIZE_MAX 275The minimum size of the 276.Fa buffer 277passed to 278.Xr getpwnam_r 3 279and 280.Xr getpwuid_r 3 . 281.It Li _SC_NPROCESSORS_CONF 282The number of processors configured. 283.It Li _SC_NPROCESSORS_ONLN 284The number of processors online (capable of running processes). 285.El 286.Sh RETURN VALUES 287If the call to 288.Nm sysconf 289is not successful, \-1 is returned and 290.Va errno 291is set appropriately. 292Otherwise, if the variable is associated with functionality that is not 293supported, \-1 is returned and 294.Va errno 295is not modified. 296Otherwise, the current variable value is returned. 297.Sh ERRORS 298The 299.Fn sysconf 300function may fail and set 301.Va errno 302for any of the errors specified for the library functions 303.Xr sysctl 3 . 304In addition, the following error may be reported: 305.Bl -tag -width Er 306.It Bq Er EINVAL 307The value of the 308.Fa name 309argument is invalid. 310.El 311.Sh SEE ALSO 312.Xr sysctl 3 313.Sh STANDARDS 314The 315.Fn sysconf 316function conforms to 317.St -p1003.1-90 . 318The constants 319.Li _SC_NPROCESSORS_CONF 320and 321.Li _SC_NPROCESSORS_ONLN 322are not part of the standard, but are provided by many systems. 323.Sh HISTORY 324The 325.Nm sysconf 326function first appeared in 327.Bx 4.4 . 328.Sh BUGS 329The value for _SC_STREAM_MAX is a minimum maximum, and required to be 330the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 331small and misleading number. 332