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NAME    [Toc]    [Back]

     units - conversion program

SYNOPSIS    [Toc]    [Back]

     units [-f filename] [-q] [-v] from-unit to-unit

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
     for example.  It also does not handle logarithmic units such
as bels.  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

     The units program can handle numbers as well:

           You have: 60 miles/hr
           You want: km/hr
                   * 96.56064
                   / 0.010356187

           You have: 5 austriaschilling
           You want: 100 italylira
                   * 7.0357114
                   / 0.14213204

     In other words, 60 miles per hour is about 96.6 km/hr, and 5
     Schillings will get you seven 100-Lira coins.

     The options are as follows:

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

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

     -v      Prints the version number.

     from-unit to-unit
             Allows a single unit conversion to be done  directly
from the command
 line.  No prompting will occur.  The units program will
             print out only the result of this single conversion.

     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'.  If the user enters 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

           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 (at 4 C)

     mercury  pressure per unit height of mercury

     ao       Bohr radius

     AU       astronomical unit

     `Pound'  is a unit of mass.  Compound names are run together
     `poundforce' is a unit of force.  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 the
     units program will try to remove a trailing `s' or a  trailing `es' and
     check again for a match.

     All  of  these definitions can be read in the standard units
file, or you
     can supply your own file.  A unit is specified on  a  single
line by giving
     its  name  and an equivalence.  One should 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.

     Prefixes  are defined in the same way as standard units, but
with a trailing
 dash at the end of the prefix name.   Prefixes  are  applied after the
     longest  matching unit name is found; for example, ``nmile''
is taken to
     be a nautical mile rather than a nanomile.

FILES    [Toc]    [Back]

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

AUTHORS    [Toc]    [Back]

     Adrian  Mariano   (adrian@cam.cornell.edu   or   mariano@geom.umn.edu)

BUGS    [Toc]    [Back]

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

     Exponents  of units 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.

     Prefixes specified without a unit are treated as  dimensionless quantities.
  This can lead to confusion when some prefixes are also defined as
     units (e.g., m).  For example, Tera- / Giga-  is  1000,  but
one Tesla (T)
     is 10,000 Gauss (G).

     Some  non-SI  units  have multiple definitions (e.g, barrel,
calorie) and
     others have changed over time (e.g., cubit).  In particular,
     values fluctuate.

     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.

OpenBSD     3.6                           July      14,      1993
[ Back ]
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