How to use the command 'units' (with examples)

The units command is a powerful tool included in many Unix-like operating systems for converting between different units of measurement. This command is part of the GNU Units package and is incredibly useful for anyone needing quick and accurate conversions across a vast range of units, including lengths, weights, volumes, areas, speeds, byte sizes, and many more. Whether for scientific calculations, cooking, engineering, or data analysis, the units command can simplify the process of converting measurements by providing an interactive mode and command-line query feature.

Use case 1: Run in interactive mode

Code:

units

Motivation: Interactive mode in the units command is useful when you need to perform multiple conversions in a single session. Instead of running separate commands for each conversion, you can enter interactive mode, do several conversions consecutively, and explore various unit equivalencies without leaving the mode.

Explanation: When you run units without any additional arguments, it enters the interactive mode. You can then input conversion queries, and the tool will keep you there until you exit manually, typically by typing “quit” or pressing Ctrl+D.

Example output:

You have: meters
You want: yards
        * 1.0936133
        / 0.9144
You have: quit

Use case 2: List all units containing a specific string in interactive mode

Code:

search string

Motivation: Searching for a specific string is particularly useful if you are unsure of the exact name or spelling of the unit you need. By searching for a substring, you can find relevant units that contain that string, making it easier to choose the correct units for conversion.

Explanation: search string is a command used within the interactive mode. “string” is a placeholder for the sequence of characters you are searching for. This command scans through the list of units available and returns any that include the substring.

Example output:

You have: search ton
floatation
metricton
percherton
USdryton
longton
shortton

Use case 3: Show the conversion between two simple units

Code:

units quarts tablespoons

Motivation: This example is applicable in culinary contexts where such conversions are often required. When following or scaling recipes, it’s crucial to accurately convert quantities between units like quarts and tablespoons to ensure the desired outcome.

Explanation: “quarts” and “tablespoons” are the units being converted. The command calculates how many tablespoons are equivalent to one quart.

Example output:

        * 64
        / 0.015625

Use case 4: Convert between units with quantities

Code:

units "15 pounds" kilograms

Motivation: Including quantities with units makes real-world tasks, such as adjusting a weight measurement from pounds to kilograms, much more straightforward. This is especially useful for academic purposes or international transactions where metric measurements are needed.

Explanation: The argument "15 pounds" specifies both the quantity and the unit you start with, while “kilograms” specifies the unit to convert to. The command converts the quantity from pounds to kilograms.

Example output:

        * 6.8038856
        / 0.14681606

Use case 5: Show the conversion between two compound units

Code:

units "meters / second" "inches / hour"

Motivation: Speed and velocity are often expressed in different units, for instance, scientific results might need conversion from meters/second to inches/hour. This conversion is relevant in physics or when adjusting units for specific regional standards.

Explanation: The compound units “meters / second” and “inches / hour” indicate a rate. The command translates this rate from one compound unit to another.

Example output:

        * 141732.28
        / 7.0569e-06

Use case 6: Show the conversion between units with different dimensions

Code:

units "acres" "ft^2"

Motivation: Land measurement often varies globally, where acres might be converted into square feet for more precise planning or when integrating with another parameter in square foot measurements.

Explanation: “acres” is the original unit representing area, converted to “ft^2” (square feet) as the desired unit. This process allows you to see the relationship across different dimensional units.

Example output:

        * 43560
        / 2.2957e-05

Use case 7: Show the conversion of byte multipliers

Code:

units "15 megabytes" bytes

Motivation: This is crucial in computer science and data engineering where precise data storage calculations are necessary. It helps ensure that data sizes are handled correctly, especially where understanding byte multiples is essential.

Explanation: The input “15 megabytes” specifies the data size in megabytes, and “bytes” is the unit to which you wish to convert. This conversion allows for accurate representation of digital storage units.

Example output:

        * 15000000
        / 6.6667e-08

Conclusion:

The units command provides an invaluable service in converting between a limitless number of units across various fields. Its versatility extends to simple conversions, complex compound unit conversions, and conversions involving specified quantities. With its straightforward interface and comprehensive capability, units helps ensure accuracy and efficiency whether you are working in science, cooking, engineering, data analysis, or any other field where measurements are crucial.