gen/FreeBSD/sysconf.3

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  32 .\"     @(#)sysconf.3   8.3 (Berkeley) 4/19/94
  33 .\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.20 2003/12/23 18:42:55 trhodes Exp $
  34 .\"
  35 .Dd June 18, 2001
  36 .Dt SYSCONF 3
  37 .Os
  38 .Sh NAME
  39 .Nm sysconf
  40 .Nd get configurable system variables
  41 .Sh LIBRARY
  42 .Lb libc
  43 .Sh SYNOPSIS
  44 .In unistd.h
  45 .Ft long
  46 .Fn sysconf "int name"
  47 .Sh DESCRIPTION
  48 This interface is defined by
  49 .St -p1003.1-88 .
  50 A far more complete interface is available using
  51 .Xr sysctl 3 .
  52 .Pp
  53 The
  54 .Fn sysconf
  55 function provides a method for applications to determine the current
  56 value of a configurable system limit or option variable.
  57 The
  58 .Fa name
  59 argument specifies the system variable to be queried.
  60 Symbolic constants for each name value are found in the include file
  61 .In unistd.h .
  62 Shell programmers who need access to these parameters should use the
  63 .Xr getconf 1
  64 utility.
  65 .Pp
  66 The available values are as follows:
  67 .Pp
  68 .Bl -tag -width 6n
  69 .Pp
  70 .It Li _SC_ARG_MAX
  71 The maximum bytes of argument to
  72 .Xr execve 2 .
  73 .It Li _SC_CHILD_MAX
  74 The maximum number of simultaneous processes per user id.
  75 .It Li _SC_CLK_TCK
  76 The frequency of the statistics clock in ticks per second.
  77 .It Li _SC_IOV_MAX
  78 The maximum number of elements in the I/O vector used by
  79 .Xr readv 2 ,
  80 .Xr writev 2 ,
  81 .Xr recvmsg 2 ,
  82 and
  83 .Xr sendmsg 2 .
  84 .It Li _SC_NGROUPS_MAX
  85 The maximum number of supplemental groups.
  86 .It Li _SC_NPROCESSORS_CONF
  87 The number of processors configured.
  88 .It Li _SC_NPROCESSORS_ONLN
  89 The number of processors currently online.
  90 .It Li _SC_OPEN_MAX
  91 The maximum number of open files per user id.
  92 .It Li _SC_STREAM_MAX
  93 The minimum maximum number of streams that a process may have open
  94 at any one time.
  95 .It Li _SC_TZNAME_MAX
  96 The minimum maximum number of types supported for the name of a
  97 timezone.
  98 .It Li _SC_JOB_CONTROL
  99 Return 1 if job control is available on this system, otherwise \-1.
 100 .It Li _SC_SAVED_IDS
 101 Returns 1 if saved set-group and saved set-user ID is available,
 102 otherwise \-1.
 103 .It Li _SC_VERSION
 104 The version of
 105 .St -p1003.1
 106 with which the system
 107 attempts to comply.
 108 .It Li _SC_BC_BASE_MAX
 109 The maximum ibase/obase values in the
 110 .Xr bc 1
 111 utility.
 112 .It Li _SC_BC_DIM_MAX
 113 The maximum array size in the
 114 .Xr bc 1
 115 utility.
 116 .It Li _SC_BC_SCALE_MAX
 117 The maximum scale value in the
 118 .Xr bc 1
 119 utility.
 120 .It Li _SC_BC_STRING_MAX
 121 The maximum string length in the
 122 .Xr bc 1
 123 utility.
 124 .It Li _SC_COLL_WEIGHTS_MAX
 125 The maximum number of weights that can be assigned to any entry of
 126 the LC_COLLATE order keyword in the locale definition file.
 127 .It Li _SC_EXPR_NEST_MAX
 128 The maximum number of expressions that can be nested within
 129 parenthesis by the
 130 .Xr expr 1
 131 utility.
 132 .It Li _SC_LINE_MAX
 133 The maximum length in bytes of a text-processing utility's input
 134 line.
 135 .It Li _SC_RE_DUP_MAX
 136 The maximum number of repeated occurrences of a regular expression
 137 permitted when using interval notation.
 138 .It Li _SC_2_VERSION
 139 The version of
 140 .St -p1003.2
 141 with which the system attempts to comply.
 142 .It Li _SC_2_C_BIND
 143 Return 1 if the system's C-language development facilities support the
 144 C-Language Bindings Option, otherwise \-1.
 145 .It Li _SC_2_C_DEV
 146 Return 1 if the system supports the C-Language Development Utilities Option,
 147 otherwise \-1.
 148 .It Li _SC_2_CHAR_TERM
 149 Return 1 if the system supports at least one terminal type capable of
 150 all operations described in
 151 .St -p1003.2 ,
 152 otherwise \-1.
 153 .It Li _SC_2_FORT_DEV
 154 Return 1 if the system supports the FORTRAN Development Utilities Option,
 155 otherwise \-1.
 156 .It Li _SC_2_FORT_RUN
 157 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
 158 otherwise \-1.
 159 .It Li _SC_2_LOCALEDEF
 160 Return 1 if the system supports the creation of locales, otherwise \-1.
 161 .It Li _SC_2_SW_DEV
 162 Return 1 if the system supports the Software Development Utilities Option,
 163 otherwise \-1.
 164 .It Li _SC_2_UPE
 165 Return 1 if the system supports the User Portability Utilities Option,
 166 otherwise \-1.
 167 .El
 168 .Sh RETURN VALUES
 169 If the call to
 170 .Fn sysconf
 171 is not successful, \-1 is returned and
 172 .Va errno
 173 is set appropriately.
 174 Otherwise, if the variable is associated with functionality that is not
 175 supported, \-1 is returned and
 176 .Va errno
 177 is not modified.
 178 Otherwise, the current variable value is returned.
 179 .Sh ERRORS
 180 The
 181 .Fn sysconf
 182 function may fail and set
 183 .Va errno
 184 for any of the errors specified for the library function
 185 .Xr sysctl 3 .
 186 In addition, the following error may be reported:
 187 .Bl -tag -width Er
 188 .It Bq Er EINVAL
 189 The value of the
 190 .Fa name
 191 argument is invalid.
 192 .El
 193 .Sh SEE ALSO
 194 .Xr getconf 1 ,
 195 .Xr pathconf 2 ,
 196 .Xr confstr 3 ,
 197 .Xr sysctl 3
 198 .Sh BUGS
 199 The value for _SC_STREAM_MAX is a minimum maximum, and required to be
 200 the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
 201 small and misleading number.
 202 .Sh STANDARDS
 203 Except for the fact that values returned by
 204 .Fn sysconf
 205 may change over the lifetime of the calling process,
 206 this function conforms to
 207 .St -p1003.1-88 .
 208 .Sh HISTORY
 209 The
 210 .Fn sysconf
 211 function first appeared in
 212 .Bx 4.4 .