.TH UNITS 1
.if n .ds / /
.SH NAME
units \- conversion program
.SH SYNOPSIS
.B units
[
.B -v
]
[
.I file
]
.SH DESCRIPTION
.I Units
converts quantities expressed
in various standard scales to
their equivalents in other scales.
It works interactively in this fashion:
.IP
.EX
you have: inch
you want: cm
    * 2.54
    / 0.393701
.EE
.PP
A quantity is specified as a multiplicative combination
of units and floating point numbers.
Operators have the following precedence:
.IP
.EX
.ta \w'\fLXXXXXXXXXXXXXXX'u
\fL+\fP \fL-\fP	\f1add and subtract
\fL*\fP \fL/\fP \fL×\fP \fL÷\fP	\f1multiply and divide
catenation	multiply
\fL²\fP \fL³\fP \fL^\fP	\f1exponentiation
\fL|\fP	\f1divide
\fL(\fP ... \fL)\fP	\f1grouping
.EE
.PP
Most familiar units,
abbreviations, and metric prefixes are recognized,
together with a generous leavening of exotica
and a few constants of nature including:
.IP
.de fq
\fL\\$1\\fP	\\$2 \\$3 \\$4 \\$5 \\$6
..
.ta \w'\fLwaterXXX'u
.nf
.fq pi,\f1π\fP ratio of circumference to diameter
.fq c speed of light
.fq e charge on an electron
.fq g acceleration of gravity
.fq force same as \fLg\fP
.fq mole Avogadro's number
.fq water "pressure head per unit height of water"
.fq au astronomical unit
.fi
.PP
The
.L pound
is a unit of
mass.
Compound names are run together, e.g.
.LR lightyear .
British units that differ from their US counterparts
are prefixed thus:
.LR brgallon .
Currency is denoted
.LR belgiumfranc ,
.LR britainpound ,
etc.
.PP
The complete list of units can be found in
.BR /lib/units .
A
.I file
argument to
.I units
specifies a file to be used instead of
.BR /lib/units.
The
.B -v
flag causes
.I units
to print its entire database.
.SH EXAMPLE
.EX
you have: 15 pounds force/in²
you want: atm
    * 1.02069
    / .97973
.EE
.SH FILES
.B /lib/units
.SH SOURCE
.B /sys/src/cmd/units.y
.SH BUGS
Since
.I units
does only multiplicative scale changes,
it can convert Kelvin to Rankine but not Centigrade to
Fahrenheit.
.PP
Currency conversions are only as accurate as the last time someone
updated the database.