udunits2.texi

\input texinfo  @c -*-texinfo-*-
@c %**start of header
@setfilename udunits2.info

@include version.texi

@settitle UDUNITS @value{VERSION} Manual
@c %**end of header
@dircategory Science
@direntry
* udunits-2: (udunits2).  The Unidata package for units of physical quantities.
@end direntry
@copying
@include LICENSE
@end copying

@titlepage
@title The UDUNITS-2 Package
@author Steven R. Emmerson

@page
@vskip 0pt plus 1filll
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@end titlepage

@contents

@ifnottex
@node Top, Introduction, (dir), (dir)
@top UDUNITS-2
This manual describes the UDUNITS-2 package, which contains
a C library for units of physical quantities and a unit-definition
and value-conversion utility.

@insertcopying
@end ifnottex

@menu
* Introduction::        Introduction
* Differences::		How this package differs from the original UDUNITS
* Obtain::              Obtaining this package
* Install::             Installing this package
* Support::             Support for this package
* Database::            The unit database
* Complete Index::      Complete index
@end menu

@node Introduction, Differences, Top, Top
@chapter Introduction
@cindex Introduction

The UDUNITS-2 package provides support for units of physical quantities.
Its three main components are: 1) @ref{Top, , a C library, udunits2lib}
for units of physical quantities;
2) @ref{Top, , a utility, udunits2prog};
for obtaining the definition of a unit and for
converting numeric values between compatible units;
and 3) an extensive database of units.

@node Differences, Obtain, Introduction, Top
@chapter How This Package Differs from the Original @code{UDUNITS} Package

The @code{UDUNIT-2} package differs from the original @code{UDUNITS}
package in the following ways:
@itemize @bullet

@item @strong{Support for non-ASCII characters:}  
The original @code{UDUNITS}
package only supports the ASCII character set.  The @code{UDUNITS-2}
package supports the following character sets: ASCII, ISO 8859-1 (Latin-1),
and the UTF-8 encoding of ISO 10646 (Unicode).  This means that unit
string specifications like "@code{µ°F·Ω⁻¹}" are now supported (your
viewer must support UTF-8 to display this string correctly).

@item @strong{Support for logarithmic units:}  The unit string
specification "@code{0.1 lg(re 1 mW)}" specifies a deciBel unit with a
one milliwatt reference level.
Such units are fully integrated into the package and all meaningful
operations and conversions are supported.

@item @strong{Persistent value converters:}
It is now possible to obtain a @emph{converter} data-object, which can
be used to convert numeric values in one unit to numeric values in another,
compatible unit.  The values can be @code{float}, @code{double}, or
one-dimensional arrays of @code{float}s or @code{double}s.

@item @strong{Improved API:}  Due to the above changes, it was not
possible to keep the application programming interface (API) of the original
@code{UDUNITS} package.  The new interface, however, is easily
understood and easy to use.  To support backward comptibility,
the package does contain a version 1 C API, which uses the version 2
library.

@item @strong{XML unit database:}  The unit database is encoded using
human-readable XML rather than a custom format.  The XML
parser included in the package supports an @emph{<import>} element to
allow easy and convenient customization.

@item @strong{No Fortran or Perl API:}  Interfaces for these languages
have not yet been created.  Contact
@email{support-udunits@@unidata.ucar.edu} if you are interested in
helping to create these interfaces.

@end itemize

One thing that has not changed is that almost all unit string specifications
understood by the original @code{UDUNITS} package are also
understood by the new @code{UDUNITS-2} package.  The one exception is
the symbol @code{g}, which in the original package was associated with
standard free fall (a unit of accelleration) but which is associated
with gram in the new package.

@node Obtain, Install, Differences, Top
@chapter Obtaining this Package
@cindex obtaining this package

Get this package from its download-page at
@uref{http://www.unidata.ucar.edu/downloads/udunits/}
and unpack it in an appropriate place, e.g.,

@example
cd /usr/local/src
gunzip -c udunits-@value{VERSION}.tar.gz | pax -r
@end example

@node Install, Database, Obtain, Top
@chapter Installing this Package
@cindex installing this package

@menu
* Short::        Short intallation instructions
* Long::         Long installation instructions
* What::         What gets installed
@end menu

@node Short, Long, , Install
@section Short Installation Instructions
Not all development enviroments can build and install this package.
See the long instructions in the next section for details.

The following assumes that you are familiar with autoconf-based
package-installation.
If you're not, then follow the long instructions in the
next section.

@example
./configure [--prefix=@var{root}] [--disable-shared] [CC=@var{path}]
make
make check                      # optional; requires CUNIT installation
make install                    # also installs INFO documentation
make install-html install-pdf   # optional
make clean
@end example

By default, the installation root is @code{/usr/local}.

If you encounter problems, then follow the instructions in the
next section.

@node Long, What, Short, Install
@section Long Installation Instructions

@enumerate
@item
Go to the top-level source-directory of this package, e.g.,
@example
cd udunits-@value{VERSION}
@end example

@item
Because some @code{make} utilities cannot build this package correctly,
locate the operating system that is closest to yours in the following table
and determine the @var{make} utility that you will use.
@quotation
@include make.texi
@end quotation

@item
If necessary, clean-up from a previous installation attempt by making
the @code{distclean} target using the @var{make} utility from step 2:
@example
@var{make} distclean
@end example

@item
Because some compilers cannot build this package correctly,
locate the operating system closest to yours in the following table
and determine the compiler
that you will use and any required option for the @code{configure} script.
@quotation
@include success.texi
@end quotation

The option @code{--disable-shared} causes the build process to create
a static library only: a sharable library is not created.
This option is necessary if the @code{libtool} utility that's included
in this package can't build a sharable library using the given compiler.

The following table lists the build environments that do not work ---
so don't use them:
@quotation
@include failure.texi
@end quotation

@item
Execute the @code{configure} script.
Specify the installation prefix, the compiler from the
previous step, and any required option.
For example, if you are on an HP-UX system and want to use
the @code{/bin/c89} compiler and install under @code{/opt},
then the following command is appropriate:

@example
./configure --prefix=/opt --disable-shared CC=/bin/c89
@end example

If the installation prefix is not specified, then the default
is to install under @code{/usr/local}.

If the compiler isn't specified, then the default is to use
@code{gcc}.

@item
Build this package by making the default target using the @var{make} utility
from step 2:
@example
@var{make}
@end example

@item
If you wish to verify that this package works correctly,
then make the @code{check} target using the
@var{make} utility from step 2:
@example
@var{make} check
@end example
This step is only effective if the @code{configure} script found an
installed @code{CUNIT} unit-testing package.  If that package wasn't
found, then the above command will quickly exit without testing this
package.

@item
Install the @ref{Top, , library, udunits2lib}, 
@ref{Top, , utility, udunits2prog}, header-files, units-database, and
INFO documentation files by making 
the @code{install} target using the @var{make} utility from
step 2:
@example
@var{make} install
@end example

@item
If desired, install the HTML and PDF documentation files by making 
one or more of the following targets 
using the @var{make} utility from step 2:
@example
@var{make} install-html install-pdf
@end example

@item
Clean up by making the @code{clean} target using the @var{make} utility
from step 2:
@example
@var{make} clean
@end example
@end enumerate

@node What, , Long, Install
@section What Gets Installed

The following files are created or installed under the installation directory:

@example
bin/:
udunits2                # Unit @ref{Top, , utility, udunits2prog}

include/:
converter.h             # API for value converters
udunits2.h              # API for units

lib/:
libudunits2.a           # Static unit @ref{Top, , library, udunits2lib}
libudunits2.la          # libtool(1) reference for unit @ref{Top, , library, udunits2lib}
libudunits2.so          # Link to shared @ref{Top, , library, udunits2lib}
libudunits2.so.0        # Link to shared @ref{Top, , library, udunits2lib}
libudunits2.so.0.0.0    # Shared @ref{Top, , library, udunits2lib}

share/:
doc                     # Directory. Created if it doesn't exist
info                    # Directory. Created if it doesn't exist
udunits                 # Directory. Created if it doesn't exist

share/doc:
udunits                 # Directory. Created if it doesn't exist

share/doc/udunits:
udunits2.html           # HTML documentation on this package
udunits2lib.html        # HTML documentation on the unit @ref{Top, , library, udunits2lib}
udunits2lib.pdf         # PDF documentation on the unit @ref{Top, , library, udunits2lib}
udunits2.pdf            # PDF documentation on this package
udunits2prog.html       # HTML documentation on the unit @ref{Top, , utility, udunits2prog}
udunits2prog.pdf        # PDF documentation on the unit @ref{Top, , utility, udunits2prog}

share/info:
dir                     # Top-level "info" file.  Created if it doesn't exist
udunits2.info           # INFO documentation on this package
udunits2lib.info        # INFO documentation on the unit @ref{Top, , library, udunits2lib}
udunits2prog.info       # INFO documentation on the unit @ref{Top, , utility, udunits2prog}

share/udunits:
udunits2.xml            # Default unit database
udunits2-accepted.xml   # Units accepted for use with the SI
udunits2-base.xml       # SI base units
udunits2-common.xml     # Common, non-SI units
udunits2-derived.xml    # Derived units of the SI
udunits2-prefixes.xml   # SI unit prefixes
@end example

@node Database, Support, Install, Top
@chapter The Units Database
@cindex database

The database for the UDUNITS-2 package comprises one XML file containing
unit prefixes and four XML files containing unit definitions:

@itemize
@item @uref{../../udunits/udunits2-prefixes.xml,SI unit prefixes}
@item @uref{../../udunits/udunits2-base.xml,SI base units}
@item @uref{../../udunits/udunits2-derived.xml,SI derived units}
@item @uref{../../udunits/udunits2-accepted.xml,Units accepted for use with the SI}
@item @uref{../../udunits/udunits2-common.xml,Non-SI units}
@end itemize

@node Support, Complete Index, Database, Top
@chapter Support for this Package
@cindex support
@cindex package, support

The home-page for this package can be found at
@uref{http://www.unidata.ucar.edu/software/udunits/}.

Bug reports should be sent to
@email{support-udunits@@unidata.ucar.edu}.

@node Complete Index, , Support, Top
@unnumbered Index

@printindex cp

@bye