How to Use the 'qr' Command to Generate QR Codes (with examples)
The ‘qr’ command is a versatile tool for generating QR codes directly in the terminal using ANSI VT-100 escape codes. This capability is particularly beneficial for quick access to QR codes without the need for a graphical user interface. The command is part of the ‘python-qrcode’ package, which is a Python library designed to generate QR codes easily. This article will explore two primary use cases for the ‘qr’ command: generating a basic QR code and specifying the error correction level for a QR code.
Generate a QR Code
Code:
echo "data" | qr
Motivation:
In today’s digital age, QR codes are ubiquitous and serve various purposes, from encoding URL links to storing various types of data. Generating QR codes in the terminal can be particularly useful for developers or tech enthusiasts working on servers or in environments where graphical interfaces aren’t available. This capability allows for quick testing and verification of QR codes.
Explanation:
echo "data": This command outputs the string “data”. In a real-world scenario, “data” can be replaced with any string you wish to encode into a QR code. This can be a URL, a piece of text, or any other type of data that you need to represent.|: The pipe symbol is used to pass the output of theechocommand as input to theqrcommand. This chaining of commands is a powerful feature of shell environments, allowing for efficient data processing.qr: This command generates the QR code in the terminal from the input data. It interprets the data it receives and converts it into QR code format, displaying it using ANSI escape codes which can be rendered in the terminal.
Example Output:
The terminal would output a matrix-like pattern representing the QR code. This pattern can be scanned using a QR code reader to retrieve the embedded data, which in this example, is the string “data”.
Specify the Error Correction Level
Code:
echo "data" | qr --error-correction=H
Motivation:
QR codes are often subjected to various degrees of distortion, damage, or occlusion. Error correction levels in QR codes are crucial for ensuring the robustness of the data against potential errors. By specifying a higher error correction level, the QR code can still be read even if it suffers physical damage or partial obstruction. This feature is particularly valuable in retail environments, printed materials, or any situation where the QR code might not be perfectly preserved.
Explanation:
echo "data": Similar to the previous use case, this echoes the string “data”, intended to be encoded into a QR code. This string is where you can input your desired data, like URLs or other informative messages.|: Again, the pipe symbol is used to funnel the output from the echo command into theqrcommand. This efficiently connects multiple command outputs and inputs in a compact manner.qr --error-correction=H: Here, theqrcommand includes an additional argument,--error-correction=H, to specify the error correction level of the QR code. Error correction levels are designated by letters: L (7% error recovery), M (15% error recovery), Q (25% error recovery), and H (30% error recovery). In this instance, the level is set to ‘H’, offering the highest protection against data loss.
Example Output:
The output is similar to the previous example, but the QR code would now contain additional error correction capability. Despite these error-correcting codes taking up more space, the QR code would be much more resilient to damage or smudges, still allowing the data to be retrieved with ease.
Conclusion
The ‘qr’ command is an invaluable tool for efficiently generating QR codes directly within the terminal. Whether for quick-testing URLs, secure data embedding, or robust encoding with superior error correction, this command provides a user-friendly approach to creating QR codes without leaving the command-line environment. By leveraging these use cases, users can effortlessly incorporate QR code generation into their workflows, enhancing productivity and accessibility.
