1 .\" $FreeBSD: src/usr.bin/units/units.1,v 1.18 2005/02/13 22:25:25 ru Exp $
2 .\" $DragonFly: src/usr.bin/units/units.1,v 1.4 2008/08/12 09:28:22 matthias Exp $
13 .Op Ar from-unit to-unit
15 The following options are available:
16 .Bl -tag -width indent
18 Specify the name of the units data file to load.
20 Suppress prompting of the user for units and the display of statistics
21 about the number of units loaded.
23 Print the version number.
24 .It Ar from-unit to-unit
25 Allow a single unit conversion to be done directly from the command
27 The program will not print prompts.
29 result of the single specified conversion.
34 program converts quantities expressed in various scales to
35 their equivalents in other scales.
39 handle multiplicative scale changes.
40 It cannot convert Celsius
41 to Fahrenheit, for example.
42 It works interactively by prompting
56 You want: furlongs/fortnight
66 Powers of units can be specified using the '^' character as shown in
67 the example, or by simple concatenation: 'cm3' is equivalent to 'cm^3'.
68 Multiplication of units can be specified by using spaces, a dash or
70 Division of units is indicated by the slash ('/').
71 Note that multiplication has a higher precedence than division,
72 so 'm/s/s' is the same as 'm/s^2' or 'm/s s'.
74 must be indicated using the vertical bar ('|').
76 meter, you would write '1|2 meter'.
77 If you write '1/2 meter' then the
78 units program would interpret that as equivalent to '0.5/meter'.
79 If you enter incompatible unit types, the units program will
80 print a message indicating that the units are not conformable and
81 it will display the reduced form for each unit:
84 You want: fathoms kg^2 / day
86 2.7777778e-11 kg m^2 / sec^3
87 2.1166667e-05 kg^2 m / sec
90 The conversion information is read from a units data file.
92 file includes definitions for most familiar units, abbreviations and
94 Some constants of nature included are:
96 .Bl -column -offset indent -compact "mercury"
97 .It "pi ratio of circumference to diameter
99 .It "e charge on an electron
100 .It "g acceleration of gravity
102 .It "mole Avogadro's number
103 .It "water pressure per unit height of water
104 .It "mercury pressure per unit height of mercury
105 .It "au astronomical unit
108 The unit 'pound' is a unit of mass.
109 Compound names are run together
110 so 'pound force' is a unit of force.
111 The unit 'ounce' is also a unit
113 The fluid ounce is 'floz'.
114 British units that differ from
115 their US counterparts are prefixed with 'br', and currency is prefixed
116 with its country name: 'belgiumfranc', 'britainpound'.
118 for a unit, if the specified string does not appear exactly as a unit
121 will try to remove a trailing 's' or a
122 trailing 'es' and check again for a match.
124 To find out what units are available read the standard units file.
125 If you want to add your own units you can supply your own file.
126 A unit is specified on a single line by
127 giving its name and an equivalence.
129 new units in terms of old ones so that a reduction leads to the
130 primitive units which are marked with '!' characters.
133 program will not detect infinite loops that could be caused
134 by careless unit definitions.
135 Comments in the unit definition file
136 begin with a '/' character at the beginning of a line.
138 Prefixes are defined in the same was as standard units, but with
139 a trailing dash at the end of the prefix name.
140 If a unit is not found
141 even after removing trailing 's' or 'es', then it will be checked
142 against the list of prefixes.
143 Prefixes will be removed until a legal
144 base unit is identified.
146 Here is an example of a short units file that defines some basic
149 .Bl -column -offset indent -compact "minute"
160 .Bl -tag -width /usr/share/misc/units.lib -compact
161 .It Pa /usr/share/misc/units.lib
162 the standard units library
165 .An Adrian Mariano Aq adrian@cam.cornell.edu
167 The effect of including a '/' in a prefix is surprising.
169 Exponents entered by the user can be only one digit.
170 You can work around this by multiplying several terms.
172 The user must use | to indicate division of numbers and / to
173 indicate division of symbols.
174 This distinction should not
177 The program contains various arbitrary limits on the length
178 of the units converted and on the length of the data file.
180 The program should use a hash table to store units so that
181 it does not take so long to load the units list and check