misc_cmds/units/units.1

   1 .\" $FreeBSD: src/usr.bin/units/units.1,v 1.18.22.1.2.1 2009/10/25 01:10:29 kensmith Exp $
   2 .Dd July 14, 1993
   3 .Dt UNITS 1
   4 .Os
   5 .Sh NAME
   6 .Nm units
   7 .Nd conversion program
   8 .Sh SYNOPSIS
   9 .Nm
  10 .Op Fl f Ar filename
  11 .Op Fl qv
  12 .Op Ar from-unit to-unit
  13 .Sh OPTIONS
  14 The following options are available:
  15 .Bl -tag -width indent
  16 .It Fl f Ar filename
  17 Specify the name of the units data file to load.
  18 .It Fl q
  19 Suppress prompting of the user for units and the display of statistics
  20 about the number of units loaded.
  21 .It Fl v
  22 Print the version number.
  23 .It Ar from-unit to-unit
  24 Allow a single unit conversion to be done directly from the command
  25 line.
  26 The program will not print prompts.
  27 It will print out the
  28 result of the single specified conversion.
  29 .El
  30 .Sh DESCRIPTION
  31 The
  32 .Nm
  33 program converts quantities expressed in various scales to
  34 their equivalents in other scales.
  35 The
  36 .Nm
  37 program can only
  38 handle multiplicative scale changes.
  39 It cannot convert Celsius
  40 to Fahrenheit, for example.
  41 It works interactively by prompting
  42 the user for input:
  43 .Bd -literal
  44     You have: meters
  45     You want: feet
  46             * 3.2808399
  47             / 0.3048
  48
  49     You have: cm^3
  50     You want: gallons
  51             * 0.00026417205
  52             / 3785.4118
  53
  54     You have: meters/s
  55     You want: furlongs/fortnight
  56             * 6012.8848
  57             / 0.00016630952
  58
  59     You have: 1|2 inch
  60     You want: cm
  61             * 1.27
  62             / 0.78740157
  63 .Ed
  64 .Pp
  65 Powers of units can be specified using the '^' character as shown in
  66 the example, or by simple concatenation: 'cm3' is equivalent to 'cm^3'.
  67 Multiplication of units can be specified by using spaces, a dash or
  68 an asterisk.
  69 Division of units is indicated by the slash ('/').
  70 Note that multiplication has a higher precedence than division,
  71 so 'm/s/s' is the same as 'm/s^2' or 'm/s s'.
  72 Division of numbers
  73 must be indicated using the vertical bar ('|').
  74 To convert half a
  75 meter, you would write '1|2 meter'.
  76 If you write '1/2 meter' then the
  77 units program would interpret that as equivalent to '0.5/meter'.
  78 If you enter incompatible unit types, the units program will
  79 print a message indicating that the units are not conformable and
  80 it will display the reduced form for each unit:
  81 .Bd -literal
  82     You have: ergs/hour
  83     You want: fathoms kg^2 / day
  84     conformability error
  85             2.7777778e-11 kg m^2 / sec^3
  86             2.1166667e-05 kg^2 m / sec
  87 .Ed
  88 .Pp
  89 The conversion information is read from a units data file.
  90 The default
  91 file includes definitions for most familiar units, abbreviations and
  92 metric prefixes.
  93 Some constants of nature included are:
  94 .Pp
  95 .Bl -column -offset indent -compact "mercury"
  96 .It "pi ratio of circumference to diameter
  97 .It "c  speed of light
  98 .It "e  charge on an electron
  99 .It "g  acceleration of gravity
 100 .It "force      same as g
 101 .It "mole       Avogadro's number
 102 .It "water      pressure per unit height of water
 103 .It "mercury    pressure per unit height of mercury
 104 .It "au astronomical unit
 105 .El
 106 .Pp
 107 The unit 'pound' is a unit of mass.
 108 Compound names are run together
 109 so 'pound force' is a unit of force.
 110 The unit 'ounce' is also a unit
 111 of mass.
 112 The fluid ounce is 'floz'.
 113 British units that differ from
 114 their US counterparts are prefixed with 'br', and currency is prefixed
 115 with its country name: 'belgiumfranc', 'britainpound'.
 116 When searching
 117 for a unit, if the specified string does not appear exactly as a unit
 118 name, then
 119 .Nm
 120 will try to remove a trailing 's' or a
 121 trailing 'es' and check again for a match.
 122 .Pp
 123 To find out what units are available read the standard units file.
 124 If you want to add your own units you can supply your own file.
 125 A unit is specified on a single line by
 126 giving its name and an equivalence.
 127 Be careful to define
 128 new units in terms of old ones so that a reduction leads to the
 129 primitive units which are marked with '!' characters.
 130 The
 131 .Nm
 132 program will not detect infinite loops that could be caused
 133 by careless unit definitions.
 134 Comments in the unit definition file
 135 begin with a '/' character at the beginning of a line.
 136 .Pp
 137 Prefixes are defined in the same was as standard units, but with
 138 a trailing dash at the end of the prefix name.
 139 If a unit is not found
 140 even after removing trailing 's' or 'es', then it will be checked
 141 against the list of prefixes.
 142 Prefixes will be removed until a legal
 143 base unit is identified.
 144 .Pp
 145 Here is an example of a short units file that defines some basic
 146 units.
 147 .Pp
 148 .Bl -column -offset indent -compact "minute"
 149 .It "m  !a!
 150 .It "sec        !b!
 151 .It "micro-     1e-6
 152 .It "minute     60 sec
 153 .It "hour       60 min
 154 .It "inch       0.0254 m
 155 .It "ft 12 inches
 156 .It "mile       5280 ft
 157 .El
 158 .Sh FILES
 159 .Bl -tag -width /usr/share/misc/units.lib -compact
 160 .It Pa /usr/share/misc/units.lib
 161 the standard units library
 162 .El
 163 .Sh AUTHORS
 164 .An Adrian Mariano Aq adrian@cam.cornell.edu
 165 .Sh BUGS
 166 The effect of including a '/' in a prefix is surprising.
 167 .Pp
 168 Exponents entered by the user can be only one digit.
 169 You can work around this by multiplying several terms.
 170 .Pp
 171 The user must use | to indicate division of numbers and / to
 172 indicate division of symbols.
 173 This distinction should not
 174 be necessary.
 175 .Pp
 176 The program contains various arbitrary limits on the length
 177 of the units converted and on the length of the data file.
 178 .Pp
 179 The program should use a hash table to store units so that
 180 it does not take so long to load the units list and check
 181 for duplication.