gen/FreeBSD/sysconf.3

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  28 .\"     @(#)sysconf.3   8.3 (Berkeley) 4/19/94
  29 .\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.25 2007/01/09 00:27:55 imp Exp $
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  31 .Dd December 14, 2006
  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
  44 This interface is defined by
  45 .St -p1003.1-88 .
  46 A far more complete interface is available using
  47 .Xr sysctl 3 .
  48 .Pp
  49 The
  50 .Fn sysconf
  51 function provides a method for applications to determine the current
  52 value of a configurable system limit or option variable.
  53 The
  54 .Fa name
  55 argument specifies the system variable to be queried.
  56 Symbolic constants for each name value are found in the include file
  57 .In unistd.h .
  58 Shell programmers who need access to these parameters should use the
  59 .Xr getconf 1
  60 utility.
  61 .Pp
  62 The available values are as follows:
  63 .Pp
  64 .Bl -tag -width 6n
  65 .Pp
  66 .It Li _SC_ARG_MAX
  67 The maximum bytes of argument to
  68 .Xr execve 2 .
  69 .It Li _SC_CHILD_MAX
  70 The maximum number of simultaneous processes per user id.
  71 .It Li _SC_CLK_TCK
  72 The frequency of the statistics clock in ticks per second.
  73 .It Li _SC_IOV_MAX
  74 The maximum number of elements in the I/O vector used by
  75 .Xr readv 2 ,
  76 .Xr writev 2 ,
  77 .Xr recvmsg 2 ,
  78 and
  79 .Xr sendmsg 2 .
  80 .It Li _SC_NGROUPS_MAX
  81 The maximum number of supplemental groups.
  82 .It Li _SC_NPROCESSORS_CONF
  83 The number of processors configured.
  84 .It Li _SC_NPROCESSORS_ONLN
  85 The number of processors currently online.
  86 .It Li _SC_OPEN_MAX
  87 The maximum number of open files per user id.
  88 .It Li _SC_PAGESIZE
  89 The size of a system page in bytes.
  90 .It Li _SC_STREAM_MAX
  91 The minimum maximum number of streams that a process may have open
  92 at any one time.
  93 .It Li _SC_TZNAME_MAX
  94 The minimum maximum number of types supported for the name of a
  95 timezone.
  96 .It Li _SC_JOB_CONTROL
  97 Return 1 if job control is available on this system, otherwise \-1.
  98 .It Li _SC_SAVED_IDS
  99 Returns 1 if saved set-group and saved set-user ID is available,
 100 otherwise \-1.
 101 .It Li _SC_VERSION
 102 The version of
 103 .St -p1003.1
 104 with which the system
 105 attempts to comply.
 106 .It Li _SC_BC_BASE_MAX
 107 The maximum ibase/obase values in the
 108 .Xr bc 1
 109 utility.
 110 .It Li _SC_BC_DIM_MAX
 111 The maximum array size in the
 112 .Xr bc 1
 113 utility.
 114 .It Li _SC_BC_SCALE_MAX
 115 The maximum scale value in the
 116 .Xr bc 1
 117 utility.
 118 .It Li _SC_BC_STRING_MAX
 119 The maximum string length in the
 120 .Xr bc 1
 121 utility.
 122 .It Li _SC_COLL_WEIGHTS_MAX
 123 The maximum number of weights that can be assigned to any entry of
 124 the LC_COLLATE order keyword in the locale definition file.
 125 .It Li _SC_EXPR_NEST_MAX
 126 The maximum number of expressions that can be nested within
 127 parenthesis by the
 128 .Xr expr 1
 129 utility.
 130 .It Li _SC_LINE_MAX
 131 The maximum length in bytes of a text-processing utility's input
 132 line.
 133 .It Li _SC_RE_DUP_MAX
 134 The maximum number of repeated occurrences of a regular expression
 135 permitted when using interval notation.
 136 .It Li _SC_2_VERSION
 137 The version of
 138 .St -p1003.2
 139 with which the system attempts to comply.
 140 .It Li _SC_2_C_BIND
 141 Return 1 if the system's C-language development facilities support the
 142 C-Language Bindings Option, otherwise \-1.
 143 .It Li _SC_2_C_DEV
 144 Return 1 if the system supports the C-Language Development Utilities Option,
 145 otherwise \-1.
 146 .It Li _SC_2_CHAR_TERM
 147 Return 1 if the system supports at least one terminal type capable of
 148 all operations described in
 149 .St -p1003.2 ,
 150 otherwise \-1.
 151 .It Li _SC_2_FORT_DEV
 152 Return 1 if the system supports the FORTRAN Development Utilities Option,
 153 otherwise \-1.
 154 .It Li _SC_2_FORT_RUN
 155 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
 156 otherwise \-1.
 157 .It Li _SC_2_LOCALEDEF
 158 Return 1 if the system supports the creation of locales, otherwise \-1.
 159 .It Li _SC_2_SW_DEV
 160 Return 1 if the system supports the Software Development Utilities Option,
 161 otherwise \-1.
 162 .It Li _SC_2_UPE
 163 Return 1 if the system supports the User Portability Utilities Option,
 164 otherwise \-1.
 165 .El
 166 .Pp
 167 These values also exist, but may not be standard:
 168 .Pp
 169 .Bl -tag -width 6n
 170 .Pp
 171 .It Li _SC_PHYS_PAGES
 172 The number of pages of physical memory.
 173 Note that it is possible that the product of this value and the value of
 174 .Li _SC_PAGESIZE
 175 will overflow a
 176 .Vt long
 177 in some configurations on a 32bit machine.
 178 .El
 179 .Sh RETURN VALUES
 180 If the call to
 181 .Fn sysconf
 182 is not successful, \-1 is returned and
 183 .Va errno
 184 is set appropriately.
 185 Otherwise, if the variable is associated with functionality that is not
 186 supported, \-1 is returned and
 187 .Va errno
 188 is not modified.
 189 Otherwise, the current variable value is returned.
 190 .Sh ERRORS
 191 The
 192 .Fn sysconf
 193 function may fail and set
 194 .Va errno
 195 for any of the errors specified for the library function
 196 .Xr sysctl 3 .
 197 In addition, the following error may be reported:
 198 .Bl -tag -width Er
 199 .It Bq Er EINVAL
 200 The value of the
 201 .Fa name
 202 argument is invalid.
 203 .El
 204 .Sh SEE ALSO
 205 .Xr getconf 1 ,
 206 .Xr pathconf 2 ,
 207 .Xr confstr 3 ,
 208 .Xr sysctl 3
 209 .Sh STANDARDS
 210 Except for the fact that values returned by
 211 .Fn sysconf
 212 may change over the lifetime of the calling process,
 213 this function conforms to
 214 .St -p1003.1-88 .
 215 .Sh HISTORY
 216 The
 217 .Fn sysconf
 218 function first appeared in
 219 .Bx 4.4 .
 220 .Sh BUGS
 221 The value for _SC_STREAM_MAX is a minimum maximum, and required to be
 222 the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
 223 small and misleading number.