1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)sysconf.3 8.3 (Berkeley) 04/19/94 7.\" 8.Dd 9.Dt SYSCONF 3 10.Os BSD 4 11.Sh NAME 12.Nm sysconf 13.Nd get configurable system variables 14.Sh SYNOPSIS 15.Fd #include <unistd.h> 16.Ft long 17.Fn sysconf "int name" 18.Sh DESCRIPTION 19.Pp 20This interface is defined by 21.St -p1003.1-88 . 22A far more complete interface is available using 23.Xr sysctl 3 . 24.Pp 25The 26.Fn sysconf 27function provides a method for applications to determine the current 28value of a configurable system limit or option variable. 29The 30.Fa name 31argument specifies the system variable to be queried. 32Symbolic constants for each name value are found in the include file 33.Li <unistd.h> . 34.Pp 35The available values are as follows: 36.Pp 37.Bl -tag -width "123456" 38.Pp 39.It Li _SC_ARG_MAX 40The maximum bytes of argument to 41.Xr exec 2 . 42.It Li _SC_CHILD_MAX 43The maximum number of simultaneous processes per user id. 44.It Li _SC_CLK_TCK 45Number of micro-seconds per hz tick. 46.It Li _SC_NGROUPS_MAX 47The maximum number of supplemental groups. 48.It Li _SC_OPEN_MAX 49The maximum number of open files per user id. 50.It Li _SC_STREAM_MAX 51The minimum maximum number of streams that a process may have open 52at any one time. 53.It Li _SC_TZNAME_MAX 54The minimum maximum number of types supported for the name of a 55timezone. 56.It Li _SC_JOB_CONTROL 57Return 1 if job control is available on this system, otherwise \-1. 58.It Li _SC_SAVED_IDS 59Returns 1 if saved set-group and saved set-user ID is available, 60otherwise \-1. 61.It Li _SC_VERSION 62The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 63attempts to comply. 64.It Li _SC_BC_BASE_MAX 65The maximum ibase/obase values in the 66.Xr bc 1 67utility. 68.It Li _SC_BC_DIM_MAX 69The maximum array size in the 70.Xr bc 1 71utility. 72.It Li _SC_BC_SCALE_MAX 73The maximum scale value in the 74.Xr bc 1 75utility. 76.It Li _SC_BC_STRING_MAX 77The maximum string length in the 78.Xr bc 1 79utility. 80.It Li _SC_COLL_WEIGHTS_MAX 81The maximum number of weights that can be assigned to any entry of 82the LC_COLLATE order keyword in the locale definition file. 83.It Li _SC_EXPR_NEST_MAX 84The maximum number of expressions that can be nested within 85parenthesis by the 86.Xr expr 1 87utility. 88.It Li _SC_LINE_MAX 89The maximum length in bytes of a text-processing utility's input 90line. 91.It Li _SC_RE_DUP_MAX 92The maximum number of repeated occurrences of a regular expression 93permitted when using interval notation. 94.It Li _SC_2_VERSION 95The version of POSIX 1003.2 with which the system attempts to comply. 96.It Li _SC_2_C_BIND 97Return 1 if the system's C-language development facilities support the 98C-Language Bindings Option, otherwise \-1. 99.It Li _SC_2_C_DEV 100Return 1 if the system supports the C-Language Development Utilities Option, 101otherwise \-1. 102.It Li _SC_2_CHAR_TERM 103Return 1 if the system supports at least one terminal type capable of 104all operations described in POSIX 1003.2, otherwise \-1. 105.It Li _SC_2_FORT_DEV 106Return 1 if the system supports the FORTRAN Development Utilities Option, 107otherwise \-1. 108.It Li _SC_2_FORT_RUN 109Return 1 if the system supports the FORTRAN Runtime Utilities Option, 110otherwise \-1. 111.It Li _SC_2_LOCALEDEF 112Return 1 if the system supports the creation of locales, otherwise \-1. 113.It Li _SC_2_SW_DEV 114Return 1 if the system supports the Software Development Utilities Option, 115otherwise \-1. 116.It Li _SC_2_UPE 117Return 1 if the system supports the User Portability Utilities Option, 118otherwise \-1. 119.El 120.Sh RETURN VALUES 121If the call to 122.Nm sysconf 123is not successful, \-1 is returned and 124.Va errno 125is set appropriately. 126Otherwise, if the variable is associated with functionality that is not 127supported, \-1 is returned and 128.Va errno 129is not modified. 130Otherwise, the current variable value is returned. 131.Sh ERRORS 132The 133.Fn sysconf 134function may fail and set 135.Va errno 136for any of the errors specified for the library functions 137.Xr sysctl 3 . 138In addition, the following error may be reported: 139.Bl -tag -width Er 140.It Bq Er EINVAL 141The value of the 142.Fa name 143argument is invalid. 144.Sh SEE ALSO 145.Xr sysctl 3 146.Sh BUGS 147The value for _SC_STREAM_MAX is a minimum maximum, and required to be 148the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 149small and misleading number. 150.Sh STANDARDS 151The 152.Fn sysconf 153function conforms to 154.St -p1003.1-88 . 155.Sh HISTORY 156The 157.Nm sysconf 158function first appeared in 4.4BSD. 159