161 lines
5.1 KiB
Groff
161 lines
5.1 KiB
Groff
.\" $FreeBSD$
|
|
.Dd July 14, 1993
|
|
.Dt UNITS 1
|
|
.Os
|
|
.Sh NAME
|
|
.Nm units
|
|
.Nd conversion program
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl f Ar filename
|
|
.Op Fl qv
|
|
.Op Ar from-unit to-unit
|
|
.Sh OPTIONS
|
|
The following options are available:
|
|
.Bl -tag -width indent
|
|
.It Fl f Ar filename
|
|
Specify the name of the units data file to load.
|
|
.It Fl q
|
|
Suppress prompting of the user for units and the display of statistics
|
|
about the number of units loaded.
|
|
.It Fl v
|
|
Print the version number.
|
|
.It Ar from-unit to-unit
|
|
Allow a single unit conversion to be done directly from the command
|
|
line. The program will not print prompts. It will print out the
|
|
result of the single specified conversion.
|
|
.El
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
program converts quantities expressed in various scales to
|
|
their equivalents in other scales. The
|
|
.Nm
|
|
program can only
|
|
handle multiplicative scale changes. It cannot convert Celsius
|
|
to Fahrenheit, for example. It works interactively by prompting
|
|
the user for input:
|
|
.Bd -literal
|
|
You have: meters
|
|
You want: feet
|
|
* 3.2808399
|
|
/ 0.3048
|
|
|
|
You have: cm^3
|
|
You want: gallons
|
|
* 0.00026417205
|
|
/ 3785.4118
|
|
|
|
You have: meters/s
|
|
You want: furlongs/fortnight
|
|
* 6012.8848
|
|
/ 0.00016630952
|
|
|
|
You have: 1|2 inch
|
|
You want: cm
|
|
* 1.27
|
|
/ 0.78740157
|
|
.Ed
|
|
.Pp
|
|
Powers of units can be specified using the '^' character as shown in
|
|
the example, or by simple concatenation: 'cm3' is equivalent to 'cm^3'.
|
|
Multiplication of units can be specified by using spaces, a dash or
|
|
an asterisk. Division of units is indicated by the slash ('/').
|
|
Note that multiplication has a higher precedence than division,
|
|
so 'm/s/s' is the same as 'm/s^2' or 'm/s s'. Division of numbers
|
|
must be indicated using the vertical bar ('|'). To convert half a
|
|
meter, you would write '1|2 meter'. If you write '1/2 meter' then the
|
|
units program would interpret that as equivalent to '0.5/meter'.
|
|
If you enter incompatible unit types, the units program will
|
|
print a message indicating that the units are not conformable and
|
|
it will display the reduced form for each unit:
|
|
.Bd -literal
|
|
You have: ergs/hour
|
|
You want: fathoms kg^2 / day
|
|
conformability error
|
|
2.7777778e-11 kg m^2 / sec^3
|
|
2.1166667e-05 kg^2 m / sec
|
|
.Ed
|
|
.Pp
|
|
The conversion information is read from a units data file. The default
|
|
file includes definitions for most familiar units, abbreviations and
|
|
metric prefixes. Some constants of nature included are:
|
|
.Pp
|
|
.Bl -inset -offset indent -compact
|
|
.It "pi ratio of circumference to diameter
|
|
.It "c speed of light
|
|
.It "e charge on an electron
|
|
.It "g acceleration of gravity
|
|
.It "force same as g
|
|
.It "mole Avogadro's number
|
|
.It "water pressure per unit height of water
|
|
.It "mercury pressure per unit height of mercury
|
|
.It "au astronomical unit
|
|
.El
|
|
.Pp
|
|
The unit 'pound' is a unit of mass. Compound names are run together
|
|
so 'pound force' is a unit of force. The unit 'ounce' is also a unit
|
|
of mass. The fluid ounce is 'floz'. British units that differ from
|
|
their US counterparts are prefixed with 'br', and currency is prefixed
|
|
with its country name: 'belgiumfranc', 'britainpound'. When searching
|
|
for a unit, if the specified string does not appear exactly as a unit
|
|
name, then
|
|
.Nm
|
|
will try to remove a trailing 's' or a
|
|
trailing 'es' and check again for a match.
|
|
.Pp
|
|
To find out what units are available read the standard units file.
|
|
If you want to add your own units you can supply your own file.
|
|
A unit is specified on a single line by
|
|
giving its name and an equivalence. Be careful to define
|
|
new units in terms of old ones so that a reduction leads to the
|
|
primitive units which are marked with '!' characters.
|
|
The
|
|
.Nm
|
|
program will not detect infinite loops that could be caused
|
|
by careless unit definitions. Comments in the unit definition file
|
|
begin with a '/' character at the beginning of a line.
|
|
.Pp
|
|
Prefixes are defined in the same was as standard units, but with
|
|
a trailing dash at the end of the prefix name. If a unit is not found
|
|
even after removing trailing 's' or 'es', then it will be checked
|
|
against the list of prefixes. Prefixes will be removed until a legal
|
|
base unit is identified.
|
|
.Pp
|
|
Here is an example of a short units file that defines some basic
|
|
units.
|
|
.Pp
|
|
.Bl -inset -offset indent -compact
|
|
.It "m !a!
|
|
.It "sec !b!
|
|
.It "micro- 1e-6
|
|
.It "minute 60 sec
|
|
.It "hour 60 min
|
|
.It "inch 0.0254 m
|
|
.It "ft 12 inches
|
|
.It "mile 5280 ft
|
|
.El
|
|
.Sh BUGS
|
|
The effect of including a '/' in a prefix is surprising.
|
|
.Pp
|
|
Exponents entered by the user can be only one digit.
|
|
You can work around this by multiplying several terms.
|
|
.Pp
|
|
The user must use | to indicate division of numbers and / to
|
|
indicate division of symbols. This distinction should not
|
|
be necessary.
|
|
.Pp
|
|
The program contains various arbitrary limits on the length
|
|
of the units converted and on the length of the data file.
|
|
.Pp
|
|
The program should use a hash table to store units so that
|
|
it doesn't take so long to load the units list and check
|
|
for duplication.
|
|
.Sh FILES
|
|
.Bl -tag -width /usr/share/misc/units.lib -compact
|
|
.It Pa /usr/share/misc/units.lib
|
|
the standard units library
|
|
.El
|
|
.Sh AUTHORS
|
|
.An Adrian Mariano Aq adrian@cam.cornell.edu
|