UDUNITS 1.12.11 Documentation

The Unidata units library (UDUNITS-1) supports conversion of unit specifications between formatted and binary forms, arithmetic manipulation of unit specifications, and conversion of values between compatible scales of measurement.

Table of Contents

1 Introduction

A unit is the amount by which a physical quantity is measured. For example:

The UDUNITS-1 package also contains an interactive utility, udunits, which has two modes. In one mode, both an input and output unit specification are given, causing the utility to print the conversion between them:

      You have: inch
      You want: cm
        cm = inch*2.54
        cm = inch/0.393701

      You have: (15 lbs force/in)^2
      You want: atm2
        atm2 = (15 lbs force/in)^2*0.995719
        atm2 = (15 lbs force/in)^2/1.0043

      You have: celsius
      You want: fahrenheit
        fahrenheit = celsius*1.8 + 32
        fahrenheit = celsius/0.555556 + 32
    

In the other mode, only an input unit specification is given. This causes the utility to print the definition -- in standard units -- of the input unit:

      You have: fahrenheit
      You want:
          Definition: "0.555556 kelvin @ 255.372"

      You have: geopotential meters
      You want:
          Definition: "9.80665 meter2 second-2"
    

2 Release Notes

See the UDUNITS-1 RELEASE NOTES file for a list of changed between versions.

3 Installation

1. Download UDUNITS-1 by browsing to the Unidata downloads page at https://downloads.unidata.ucar.edu/udunits/.
2. Follow the installation instructions outlined in the INSTALL file.

4 Supported Units

View the Supported Units for UDUNITS-1.

5 Man Pages

Further information on the UDUNITS-1 package can be found in the following man pages:

• C manual page
• FORTRAN manual page
• Utility manual page

6 Support For This Package

• View Current Support Questions being asked of the UDUNITS developer.
• Use the UDUNITS Mailing Lista> to query experts in the Unidata community
• Bug reports and support questions should be sent to support-udunits@unidata.ucar.edu.

7 License

Copyright 2023 University Corporation for Atmospheric Research and contributors. All rights reserved.

This software was developed by the Unidata Program Center of the University Corporation for Atmospheric Research (UCAR) https://www.unidata.ucar.edu.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
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3. Neither the names of the development group, the copyright holders, nor the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission.
4. This license shall terminate automatically, and you may no longer exercise any of the rights granted to you by this license as of the date you commence an action, including a cross-claim or counterclaim, against the copyright holders or any contributor alleging that this software infringes a patent. This termination provision shall not apply for an action alleging patent infringement by combinations of this software with other software or hardware.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE SOFTWARE.