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NAME    [Toc]    [Back]

     units -- conversion program

SYNOPSIS    [Toc]    [Back]

     units [-f filename] [-qv] [from-unit to-unit]

OPTIONS    [Toc]    [Back]

     The following options are available:

     -f filename
	     Specify the name of the units data file to load.

     -q      Suppress prompting of the user for units and the display of statistics
 about the number of units loaded.

     -v      Print the version number.

     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.

DESCRIPTION    [Toc]    [Back]

     The units program converts quantities expressed in various scales to
     their equivalents in other scales.  The units program can only handle
     multiplicative scale changes.  It cannot convert Celsius to Fahrenheit,
     for example.  It works interactively by prompting the user for input:

	 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

     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:

	 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

     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:

	   pi	   ratio of circumference to diameter
	   c	   speed of light
	   e	   charge on an electron
	   g	   acceleration of gravity
	   force   same as g
	   mole    Avogadro's number
	   water   pressure per unit height of water
	   mercury pressure per unit height of mercury
	   au	   astronomical unit

     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
     units will try to remove a trailing 's' or a trailing 'es' and check
     again for a match.

     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
     units 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.

     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

     Here is an example of a short units file that defines some basic units.

	   m	   !a!
	   sec	   !b!
	   micro-  1e-6
	   minute  60 sec
	   hour    60 min
	   inch    0.0254 m
	   ft	   12 inches
	   mile    5280 ft

BUGS    [Toc]    [Back]

     The effect of including a '/' in a prefix is surprising.

     Exponents entered by the user can be only one digit.  You can work around
     this by multiplying several terms.

     The user must use | to indicate division of numbers and / to indicate
     division of symbols.  This distinction should not be necessary.

     The program contains various arbitrary limits on the length of the units
     converted and on the length of the data file.

     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.

FILES    [Toc]    [Back]

     /usr/share/misc/units.lib	the standard units library

AUTHORS    [Toc]    [Back]

     Adrian Mariano <adrian@cam.cornell.edu>

FreeBSD 5.2.1			 July 14, 1993			 FreeBSD 5.2.1
[ Back ]
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