gen/sysconf.3

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  32 .\"     @(#)sysconf.3   8.3 (Berkeley) 4/19/94
  33 .\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.16 2001/10/01 16:08:51 ru Exp $
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  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 .Aq Pa 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_OPEN_MAX
  87 The maximum number of open files per user id.
  88 .It Li _SC_STREAM_MAX
  89 The minimum maximum number of streams that a process may have open
  90 at any one time.
  91 .It Li _SC_TZNAME_MAX
  92 The minimum maximum number of types supported for the name of a
  93 timezone.
  94 .It Li _SC_JOB_CONTROL
  95 Return 1 if job control is available on this system, otherwise \-1.
  96 .It Li _SC_SAVED_IDS
  97 Returns 1 if saved set-group and saved set-user ID is available,
  98 otherwise \-1.
  99 .It Li _SC_VERSION
 100 The version of
 101 .St -p1003.1
 102 with which the system
 103 attempts to comply.
 104 .It Li _SC_BC_BASE_MAX
 105 The maximum ibase/obase values in the
 106 .Xr bc 1
 107 utility.
 108 .It Li _SC_BC_DIM_MAX
 109 The maximum array size in the
 110 .Xr bc 1
 111 utility.
 112 .It Li _SC_BC_SCALE_MAX
 113 The maximum scale value in the
 114 .Xr bc 1
 115 utility.
 116 .It Li _SC_BC_STRING_MAX
 117 The maximum string length in the
 118 .Xr bc 1
 119 utility.
 120 .It Li _SC_COLL_WEIGHTS_MAX
 121 The maximum number of weights that can be assigned to any entry of
 122 the LC_COLLATE order keyword in the locale definition file.
 123 .It Li _SC_EXPR_NEST_MAX
 124 The maximum number of expressions that can be nested within
 125 parenthesis by the
 126 .Xr expr 1
 127 utility.
 128 .It Li _SC_LINE_MAX
 129 The maximum length in bytes of a text-processing utility's input
 130 line.
 131 .It Li _SC_RE_DUP_MAX
 132 The maximum number of repeated occurrences of a regular expression
 133 permitted when using interval notation.
 134 .It Li _SC_2_VERSION
 135 The version of
 136 .St -p1003.2
 137 with which the system attempts to comply.
 138 .It Li _SC_2_C_BIND
 139 Return 1 if the system's C-language development facilities support the
 140 C-Language Bindings Option, otherwise \-1.
 141 .It Li _SC_2_C_DEV
 142 Return 1 if the system supports the C-Language Development Utilities Option,
 143 otherwise \-1.
 144 .It Li _SC_2_CHAR_TERM
 145 Return 1 if the system supports at least one terminal type capable of
 146 all operations described in
 147 .St -p1003.2 ,
 148 otherwise \-1.
 149 .It Li _SC_2_FORT_DEV
 150 Return 1 if the system supports the FORTRAN Development Utilities Option,
 151 otherwise \-1.
 152 .It Li _SC_2_FORT_RUN
 153 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
 154 otherwise \-1.
 155 .It Li _SC_2_LOCALEDEF
 156 Return 1 if the system supports the creation of locales, otherwise \-1.
 157 .It Li _SC_2_SW_DEV
 158 Return 1 if the system supports the Software Development Utilities Option,
 159 otherwise \-1.
 160 .It Li _SC_2_UPE
 161 Return 1 if the system supports the User Portability Utilities Option,
 162 otherwise \-1.
 163 .El
 164 .Sh RETURN VALUES
 165 If the call to
 166 .Fn sysconf
 167 is not successful, \-1 is returned and
 168 .Va errno
 169 is set appropriately.
 170 Otherwise, if the variable is associated with functionality that is not
 171 supported, \-1 is returned and
 172 .Va errno
 173 is not modified.
 174 Otherwise, the current variable value is returned.
 175 .Sh ERRORS
 176 The
 177 .Fn sysconf
 178 function may fail and set
 179 .Va errno
 180 for any of the errors specified for the library function
 181 .Xr sysctl 3 .
 182 In addition, the following error may be reported:
 183 .Bl -tag -width Er
 184 .It Bq Er EINVAL
 185 The value of the
 186 .Fa name
 187 argument is invalid.
 188 .El
 189 .Sh SEE ALSO
 190 .Xr getconf 1 ,
 191 .Xr pathconf 2 ,
 192 .Xr confstr 3 ,
 193 .Xr sysctl 3
 194 .Sh BUGS
 195 The value for _SC_STREAM_MAX is a minimum maximum, and required to be
 196 the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
 197 small and misleading number.
 198 .Sh STANDARDS
 199 Except for the fact that values returned by
 200 .Fn sysconf
 201 may change over the lifetime of the calling process,
 202 this function conforms to
 203 .St -p1003.1-88 .
 204 .Sh HISTORY
 205 The
 206 .Fn sysconf
 207 function first appeared in
 208 .Bx 4.4 .