NAME
units-filter - is a parser for physical and chemical quantities
SYNOPSIS
units-filter -s -o -l
DESCRIPTION
units-filter is a basic standalone parser written in C language, flex
and bison. It inputs strings like "1.5e3 nN.m.s^-1" (it could be the
time growth ratio of a torque) and outputs the value in standard SI
unit, followed by the physical dimension of this value.
OPTIONS
-s
Like Significative.
Takes in account the number of significative digits. For example
1.0 m contains 2 significative digits, while 0.00100 contains 3
significative digits. It is possible to enforce the number of
significative digits by using a special syntax : if units-filter
parses the input "1.0m#6", it interprets it as a value with exactly
6 significative digits, like "1.00000 m". The number following the
# sign is the forced number of significative digits. The number of
significative digits appears just before the last zero in the
output of the command (this zero is a placeholder for future
extensions).
-o
Like Output.
Outputs a correct representation of the physical quantity with its
physical unit in the International System notation. There may be
some simplification with usual units. For example, a newton will be
represented by the unit N in place of m.kg.s^-2. The value is
expressed as a floating number with one digit before the decimal
point, and as many digits in the mantissa as necessary to fit the
desired number of significative digits (see an example below). It
is possible to enforce the output unit : just add a colon and the
desired unit at the end of the input. If this unit is homogeneous
with the former one, it will be used to format the output.
-l
Like LaTeX.
Outputs a correct representation of the physical quantity with its
physical unit in the International System notation, in LaTeX
language.
EXAMPLES
Establishing the SI value and units exponents of a quantity in the mksa
system:
~$ echo 1.5e3 nN.m.s^-1 | units-filter
1.5e-6 2 1 -3 0 0 0 0
which means : 1.5e-6 (SI unit) m^2.kg.s^-3
Comparing to different physical quantities:
~$ e1=$(echo "1.2e-3 V" | units-filter)
~$ e2=$(echo "1200e3 nWb/s"| units-filter)
~$ if [ "$e1" = "$e2" ]; then echo ok; else echo ko; fi
ok
... which emphasizes that webers by unit time are the same than volts.
Playing with the number of significative digits:
~$ echo "0.00100m" | src/units-filter -s
0.001 1 0 0 0 0 0 0 3 0
~$ echo "0.00100m #2" | src/units-filter -s
0.001 1 0 0 0 0 0 0 2 0
Giving a value for the relative precision:
~$ echo "1kV~2" | units-filter -o
1e+03 V +-2%
Turning on the LaTeX output:
~$ echo "1kohm+-2%" | units-filter -l
1\times 10^{+03}\, \Omega \pm 2\,\%
Turning on the output of a canonical physical notation:
~$ echo "1.0 m.kg.s^-2 #7" | units-filter -o
1.000000e+00N
Choosing a non-standard unit for the output:
~$ echo 1800C:A.h| units-filter -o
5.000e-01 A.h
KNOWN BUGS
Few units out of the mksa system are sucessfuly parsed.
AUTHOR
Georges Khaznadar <georgesk@ofset.org>
Wrote this manpage.
COPYRIGHT
Copyright © 2009 Georges Khaznadar
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU General Public License, Version 2 or (at
your option) any later version published by the Free Software
Foundation.
On Debian systems, the complete text of the GNU General Public License
can be found in /usr/share/common-licenses/GPL.