This is Info file units.info, produced by Makeinfo version 1.67 from
the input file ./units.texinfo.

START-INFO-DIR-ENTRY
* units: (units).	Units conversion.
END-INFO-DIR-ENTRY

   This file documents the GNU `units' command for unit conversion.
This is edition 1.32 for `units' Version 1.54.

   Copyright (C) 1996, 1997, 1999 Free Software Foundation, Inc

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that
the entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions.


File: units.info,  Node: Top,  Up: (dir)

   This manual describes the `units' command for units conversion, and
how you can use it to convert units from one scale to another.

   This is Edition 1.32 of `The Units Conversion Manual' for `units'
Version 1.54.

* Menu:

* Overview::            What does `units' do?
* Interactive use::     How to use `units'.
* Command line use::    How to use `units' noninteractively.
* Invoking units::      Command line options.
* Unit expressions::    Forming compound units.
* Unit definitions::    What units are defined?
* Defining new units::  How to write your own units definitions.
* Readline support::    Unit name completion and editing.
* Index::               General index


File: units.info,  Node: Overview,  Next: Interactive use,  Prev: Top,  Up: Top

Overview of `units'
*******************

   The `units' program converts quantities expressed in various scales
to their equivalents in other scales.  The `units' program can only
handle multiplicative scale changes.  For example, it cannot convert
Celsius to Fahrenheit but it can convert temperature differences
between those temperature scales.

   The units are defined in an external data file.  You can use the
extensive data file that comes with this program, or you can provide
your own data file to suit your needs.

   You can use the program interactively with prompts, or you can use it
from the command line.


File: units.info,  Node: Interactive use,  Next: Command line use,  Prev: Overview,  Up: Top

Interacting with `units'
************************

   To invoke units for interactive use, type `units' at your shell
prompt.  The program will print something like this:

         1161 units, 53 prefixes
     
         You have:

At the `You have:' prompt, type the quantity and units that you are
converting *from*.  For example, if you want to convert ten meters to
feet, type `10 meters'.  Next, `units' will print `You want:'.  You
should type the type of units you want to convert *to*.  To convert to
feet, you would type `feet'.

   The answer will be displayed in two ways.  The first line of output,
which is marked with a `*' to indicate multiplication, gives the result
of the conversion you have asked for.  The second line of output, which
is marked with a `/' to indicate division, gives the inverse of the
conversion factor.  If you convert 10 meters to feet, `units' will print

             * 32.808399
             / 0.03048

which tells you that 10 meters equals about 32.8 feet.  The second
number gives the conversion in the reverse directions.  In this case,
it tells you that 1 foot is equal to about 0.03 dekameters since the
dekameter is 10 meters.  It also tells you that 1/32.8 is about .03.

   The `units' program prints the inverse because sometimes it is a
more convenient number.  In the example above, for example, the inverse
value is an exact conversion: a foot is exactly .03048 dekameters.  But
the number given the other direction is inexact.

   If you try to convert grains to pounds, you will see the following:

         You have: grains
         You want: pounds
                 * 0.00014285714
                 / 7000

From the second line of the output you can immediately see that a grain
is equal to a seven thousandth of a pound.  This is not so obvious from
the first line of the output.  If you find  the output format
confusing, try using the `--verbose' option:

         You have: grain
         You want: aeginamina
                 grain = 0.00010416667 aeginamina
                 grain = (1 / 9600) aeginamina

   If you request a conversion between units which measure reciprocal
dimensions, then `units' will display the conversion results with an
extra note indicating that reciprocal conversion has been done:

         You have: 6 ohms
         You want: siemens
                 reciprocal conversion
                 * 0.16666667
                 / 6

   Reciprocal conversion can be suppressed by using the `--strict'
option.  As usual, use the `--verbose' option to get more
comprehensible output:

         You have: tex
         You want: typp
                 reciprocal conversion
                 1 / tex = 496.05465 typp
                 1 / tex = (1 / 0.0020159069) typp
     
         You have: 20 mph
         You want: sec/mile
                 reciprocal conversion
                 1 / 20 mph = 180 sec/mile
                 1 / 20 mph = (1 / 0.0055555556) sec/mile

   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

   If you only want to find the reduced form or definition of a unit,
simply press return at the `You want:' prompt.  Here is an example:

         You have: jansky
         You want:
                 Definition: fluxunit = 1e-26 W/m^2 Hz = 1e-26 kg / s^2

The output from `units' indicates that the jansky is defined to be
equal to a fluxunit which in turn is defined to be a certain combination
of watts, meters, and hertz.  The fully reduced (and in this case
somewhat more cryptic) form appears on the far right.


File: units.info,  Node: Command line use,  Next: Unit expressions,  Prev: Interactive use,  Up: Top

Using `units' non-interactively
*******************************

   The `units' program can perform units conversions non-interactively
from the command line.  To do this, type the command, type the original
units expression, and type the new units you want.  You will probably
need to protect the units expressions from interpretation by the shell
using single quote characters.

   If you type

         units '2 liters' 'quarts'

then `units' will print

             * 2.1133764
             / 0.47317647

and then exit.  The output tells you that 2 liters is about 2.1 quarts,
or alternatively that a quart is about 0.47 times 2 liters.

   If the conversion is successful, then `units' will return success to
the calling environment.  If `units' is given non-conformable units to
convert, it will print a message giving the reduced form of each unit
and it will return failure to the calling environment.

   When `units' is invoked with only one argument, it will print out
the definition of the specified unit.  It will return failure if the
unit is not defined and success if the unit is defined.


File: units.info,  Node: Unit expressions,  Next: Invoking units,  Prev: Command line use,  Up: Top

Unit expressions
****************

   In order to enter more complicated units or fractions, you will need
to use operations such as powers, products and division.  Powers of
units can be specified using the `^' character as shown in the
following example, or by simple concatenation: `cm3' is equivalent to
`cm^3'.  If the exponent is more than one digit, the `^' is required.

         You have: cm^3
         You want: gallons
                 * 0.00026417205
                 / 3785.4118
     
         You have: arabicfoot-arabictradepound-force
         You want: ft lbf
                 * 0.7296
                 / 1.370614

   Multiplication of units can be specified by using spaces, a hyphen
(`-') or an asterisk (`*').  Division of units is indicated by the
slash (`/').

         You have: furlongs/fortnight
         You want: m/s
                 * 0.00016630986
                 / 6012.8727

   Multiplication has a higher precedence than division and is evaluated
left to right, so `m/s * s/day' is equivalent to `m / s s day' and has
dimensions of length per time cubed.  In effect, the first `/'
character marks the beginning of the denominator of your unit.  In
particular, this means that writing `1/2 meter' refers to a unit of
reciprocal length equivalent to .5/meter, which is probably not what
you would intend if you entered that expression.  To indicate division
of numbers, use the vertical dash (`|').  No spaces area permitted on
either side of the vertical dash character.

         You have: 1|2 inch
         You want: cm
                 * 1.27
                 / 0.78740157

   Prefixes are defined separately from base units.  In order to get
centimeters, the units database defines `centi-' and `c-' as prefixes.
Prefixes can appear alone with no unit following them.  An exponent
applies only to the immediately preceding unit and its prefix so that
`cm^3' or `centimeter^3' refer to cubic centimeters but `centi-meter^3'
refers to hundredths of cubic meters.  Only one prefix is permitted per
unit, so `micromicrofarad' will fail, but `micro-microfarad' will work.

   For `units', numbers are just another kind of unit.  They can appear
as many times as you like and in any order in a unit expression.  For
example, to find the volume of a box which is 2 ft by 3 ft by 12 ft in
steres, you could do the following:

         You have: 2 ft 3 ft 12 ft
         You want: stere
                 * 2.038813
                 / 0.49048148
     
         You have: $ 5 / yard
         You want: cents / inch
                 * 13.888889
                 / 0.072

And the second example shows how the dollar sign in the units conversion
can precede the five.  Be careful:  `units' will interpret `$5' with no
space as equivalent to dollars^5.

   Outside of the SI system, it is often desirable to add values of
different units together.  Sums of conformable units are written with
the `+' character.

         You have: 2 hours + 23 minutes + 32 seconds
         You want: seconds
                 * 8612
                 / 0.00011611705
     
         You have: 12 ft + 3 in
         You want: cm
                 * 373.38
                 / 0.0026782366
     
         You have: 2 btu + 450 ft-lbf
         You want: btu
                 * 2.5782804
                 / 0.38785542

The expressions which are added together must reduce to identical
expressions in primitive units, or an error message will be displayed:

         You have: 12 printerspoint + 4 heredium
         Illegal sum of non-conformable units:
                 12 printerspoint reduces to 0.0042175176 m
                 4 heredium reduces to 20145.828 m^2

Because `-' is used for products, it cannot  also be used to form
differences of units.  If a `-' appears before numerical digits as the
very first character on the input line or if it appears immediately
after a `+' then the number will be evaluated as a negative number.  So
you can compute 20 degrees minus 12 minutes by entering `20 degrees+-12
arcmin'.  The `+' character is sometimes used in exponents like
`3.43e+8'.  Exponents of this form cannot be used when forming sums of
units, but they may be used otherwise.


File: units.info,  Node: Invoking units,  Next: Unit definitions,  Prev: Unit expressions,  Up: Top

Invoking `units'
****************

   You invoke `units' like this:

         units OPTIONS [FROM-UNIT [TO-UNIT]]

If the FROM-UNIT and TO-UNIT are omitted, then the program will use
interactive prompts to determine which conversions to perform.  *Note
Interactive use::.  If both FROM-UNIT and TO-UNIT are given, `units'
will print the result of that single conversion and then exit.  If only
FROM-UNIT appears on the command line, `units' will display the
definition of that unit and exit.  Units specified on the command line
will need to be quoted to protect them from shell interpretation and to
group them into two arguments.  *Note Command line use::.

   The following options allow you to read in an alternative units file,
check your units file, or change the output format:

`-c'
`--check'
     Check that all units and prefixes defined in the units file reduce
     to primitive units.  The program will print a list of all units
     that cannot be reduced.

`--check-verbose'
     Like the `-check' option, this option prints a list of units that
     cannot be reduced.  But to help find unit  definitions that cause
     endless loops, it lists the units as they are checked.  If `units'
     hangs, then the last unit to be printed has a bad definition.

`-o format'
`--output-format format'
     Use the specified format for numeric output.  Format is the same
     as that for the printf function in the ANSI C standard.  For
     example, if you want more precision you might use `-o %.15g'.

`-f filename'
`--file filename'
     Use filename as the units data file rather than the default units
     data file.

`-h'
`--help'
     Print out a summary of the options for `units'.

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

`-s'
`--strict'
     Suppress conversion of units to their reciprocal units.

`-v'
`--verbose'
     Give slightly more verbose output when converting units.  When
     combined with the `-c' option this gives the same effect as
     `--check-verbose'.

`-V'
`--version'
     Print program version number, tell whether the readline library
     has been included, and give the location of the default units data
     file.


File: units.info,  Node: Unit definitions,  Next: Defining new units,  Prev: Invoking units,  Up: Top

Unit definitions
****************

   The conversion information is read from a units data file which is
called `units.dat' and is probably located in the `/usr/local/share'
directory.  If you invoke `units' with the `-V' option, it will print
the location of this file.  The default file includes definitions for
all familiar units, abbreviations and metric prefixes.  It also
includes many obscure or archaic units.

   Many constants of nature are defined, including these:
     pi          ratio of circumference to diameter
     c           speed of light
     e           charge on an electron
     force       acceleration of gravity
     mole        Avogadro's number
     water       pressure per unit height of water
     Hg          pressure per unit height of mercury
     au          astronomical unit
     k           Boltzman's constant
     mu0         permeability of vacuum
     epsilon0    permitivity of vacuum
     G           Gravitational constant
     mach        speed of sound

The database includes atomic masses for all of the elements and numerous
other constants.  Also included are the densities of various ingredients
used in baking so that `2 cups flour_sifted' can be converted to
`grams'.  This is not an exhaustive list.  Consult the units data file
to see the complete list, or to see the definitions that are used.

   The unit `pound' is a unit of mass.  To get force, multiply by the
force conversion unit `force' or use the shorthand `lbf'.  (Note that
`g' is already taken as the standard abbreviation for the gram.)  The
unit `ounce' is also a unit of mass.  The fluid ounce is `fluidounce'
or `floz'.  British capacity units that differ from their US
counterparts, such as the British Imperial gallon, are prefixed with
`br'.  Currency is prefixed with its country name: `belgiumfranc',
`britainpound'.

   The US Survey foot, yard, and mile can be obtained by using the `US'
prefix.  These units differ slightly from the international length
units.  They were in use until 1959, but for geographic surveys, they
are still used.  The acre is officially defined in terms of the US
Survey foot.  If you want an acre defined according to the
international foot, use `intacre'.  The difference between these units
is about 4 parts per million.  The British also used a slightly
different length measure before 1959.  These can be obtained with the
prefix `UK'.

   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'.  If that fails, `units' will check for
a prefix.  All of the standard metric prefixes are defined.

   To find out what units and prefixes are available, read the standard
units data file.


File: units.info,  Node: Defining new units,  Next: Readline support,  Prev: Unit definitions,  Up: Top

Defining new units
******************

   All of the units and prefixes that `units' can convert are defined
in the units data 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.  Comments start with a `#' character, which can appear
anywhere in a line.  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.  When adding new units, be sure to use the `-c'
option to check that the new units reduce properly.  If you define any
units which contain `+' characters, carefully check them because the
`-c' option will not catch non-conformable sums.  If you create a loop
in the units definitions, then `units' will hang when invoked with the
`-c' options.  You will need to use the `--check-verbose' option which
prints out each unit as it checks them.  The program will still hang,
but the last unit printed will be the unit which caused the infinite
loop.

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

     m       !               # The meter is a primitive unit
     sec     !               # The second is a primitive unit
     micro-  1e-6            # Define a prefix
     minute  60 sec          # A minute is 60 seconds
     hour    60 min          # An hour is 60 minutes
     inch    0.0254 m        # Inch defined in terms of meters
     ft      12 inches       # The foot defined in terms of inches
     mile    5280 ft         # And the mile

A unit which ends with a `-' character is a prefix.  If a prefix
contains a `/' character, then when it is applied to a unit, that unit
will be in the denominator.  So the definition `half- 1/2' would give a
`halfmeter' equal to `1 / 2 meter'.  For this reason, the `/' character
should be avoided in prefixes.


File: units.info,  Node: Readline support,  Prev: Defining new units,  Up: Top

Readline support
****************

   If the `readline' package has been compiled in, then when `units' is
used interactively, numerous command line editing features are
available.  To check if your version of `units' includes the readline,
invoke the program with the `--version' option.

   For complete information about readline, consult the documentation
for the readline package.  Without any configuration, `units' will
allow editing in the style of emacs.  Of particular use with `units'
are the completion commands.

   If you type a few characters and then hit `ESC' followed by the `?'
key then `units' will display a list of all the units which start with
the characters typed.  For example, if you type `metr' and then request
completion, you will see something like this:

     You have: metr
     metre             metriccup         metrichorsepower  metrictenth
     metretes          metricfifth       metricounce       metricton
     metriccarat       metricgrain       metricquart       metricyarncount
     You have: metr

If there is a unique way to complete a unitname, you can hit the tab key
and `units' will provide the rest of the unit name.  If `units' beeps,
it means that there is no unique completion.  Pressing the tab key a
second time will print the list of all completions.


File: units.info,  Node: Index,  Up: Top

Index
*****

* Menu:

* -c (option for units):                 Invoking units.
* -check (option for units):             Invoking units.
* -check-verbose (option for units):     Invoking units.
* -f (option for units):                 Invoking units.
* -file (option for units):              Invoking units.
* -h (option for units):                 Invoking units.
* -help (option for units):              Invoking units.
* -o (option for units):                 Invoking units.
* -output-format (option for units):     Invoking units.
* -q (option for units):                 Invoking units.
* -quiet (option for units):             Invoking units.
* -s (option for units):                 Invoking units.
* -silent (option for units):            Invoking units.
* -strict (option for units):            Invoking units.
* -v (option for units):                 Invoking units.
* -V (option for units):                 Invoking units.
* -verbose (option for units):           Invoking units.
* -version (option for units):           Invoking units.
* addition of units:                     Unit expressions.
* changing units definitions:            Defining new units.
* command line options:                  Invoking units.
* command line unit conversion:          Command line use.
* defining units:                        Defining new units.
* division of numbers:                   Unit expressions.
* division of units:                     Unit expressions.
* fractions:                             Unit expressions.
* incompatible units:                    Interactive use.
* interactive use:                       Interactive use.
* invoking units:                        Invoking units.
* multiplication of units:               Unit expressions.
* non-conformable units:                 Interactive use.
* non-interactive unit conversion:       Command line use.
* powers:                                Unit expressions.
* products:                              Unit expressions.
* readline, use with units:              Readline support.
* reciprocal conversion:                 Interactive use.
* strict conversion:                     Interactive use.
* sums of units:                         Unit expressions.
* unit definitions:                      Unit definitions.
* unit expressions:                      Unit expressions.
* unit name completion:                  Readline support.
* units, redefinition of:                Defining new units.
* verbose output:                        Interactive use.



Tag Table:
Node: Top926
Node: Overview1653
Node: Interactive use2359
Node: Command line use6289
Node: Unit expressions7500
Node: Invoking units11790
Node: Unit definitions14159
Node: Defining new units17029
Node: Readline support19018
Node: Index20409

End Tag Table
