Understanding 'hexyl' for Hexadecimal Viewing (with examples)

Despite the often daunting nature of analyzing binary data, the command-line tool hexyl provides a straightforward way to view files in hexadecimal format. By distinguishing byte categories with colors, hexyl simplifies the inspection of file content at a byte level. This article explores various use cases of hexyl, detailing how it can be used for different binary inspection tasks.

Use case 1: Print the hexadecimal representation of a file

Code:

hexyl path/to/file

Motivation:

The primary motivation for this use case is to provide users with a comprehensive view of an entire file in hexadecimal format. This is particularly useful for debugging, reverse engineering, or simply understanding the structure of an unknown file type. By examining the complete file, users can gain insights into its data composition and any embedded information.

Explanation:

• hexyl: This command invokes the hex viewer utility, initiating the process of converting the file’s data into a hexadecimal format.

• path/to/file: This argument specifies the path to the file whose contents you wish to inspect. Replace path/to/file with the actual file path.

Example output:

Assuming a file contains ASCII characters, the output will display lines of hexadecimal values alongside ASCII representations. Bytes are categorized and highlighted using different colors, with non-printable characters often shown as dots or squares for clarity.

Use case 2: Print the hexadecimal representation of the first n bytes of a file

Code:

hexyl -n n path/to/file

Motivation:

This use case allows users to focus on the initial segment of a file, which often contains metadata or headers crucial for understanding the file format. By examining just the beginning, one can glean initial insights without parsing the entire file, which can be especially valuable when dealing with large datasets.

Explanation:

• hexyl: Once again initiates the reading of the file in hexadecimal format.

• -n n: This option instructs hexyl to display only the first n bytes of the file. Replace n with the number of bytes you wish to view.

• path/to/file: Specifies the file to read from, again needing user specification for a concrete path.

Example output:

For a file starting with a specific pattern or magic number, you’ll see a colored, formatted output of the requested byte range, aiding quick recognition of file types or headers.

Use case 3: Print bytes 512 through 1024 of a file

Code:

hexyl -r 512:1024 path/to/file

Motivation:

Sometimes, it’s necessary to inspect a specific segment of a file instead of wading through the entire contents or just the beginning. This functionality is suitable for probing file sections that might contain different data types or structures, often necessary for things like embedded file systems or data validations.

Explanation:

• hexyl: Invokes the tool to commence the hexadecimal viewing process.

• -r 512:1024: This argument specifies a byte range. Here, 512:1024 tells hexyl to show bytes from the 512th to the 1024th. The colon : serves as a separator for the beginning and end of the range.

• path/to/file: Indicates the file from which bytes are read and viewed.

Example output:

The output will display bytes 512 to 1024 in hexadecimal representation, with distinct color coding, making specific byte patterns or anomalies easier to identify.

Use case 4: Print 512 bytes starting at the 1024th byte

Code:

hexyl -r 1024:+512 path/to/file

Motivation:

In scenarios where you might already know the location of particular data within a file, this command focuses on extracting a specific chunk starting from a known byte offset. This is particularly handy for directly accessing sections without additional calculations or unnecessary data inspection.

Explanation:

• hexyl: The tool is called to initiate the hexadecimal conversion and visualization.

• -r 1024:+512: This range indicator instructs hexyl to begin at the 1024th byte and to display the subsequent 512 bytes. The + sign indicates a finite length starting from a particular point.

• path/to/file: This argument identifies which file’s data will be analyzed and displayed.

Example output:

You’ll see an isolated 512-byte section at the specified offset rendered in hex format, with visual differentiation for easier pattern recognition.

Conclusion:

Hexyl proves to be an invaluable tool for anyone needing precise inspection and analysis of file data at the byte level. From viewing entire files to extracting specific segments, hexyl offers versatile functionalities enhanced by its color-coded visualization, making complex data easier to interpret. Whether for debugging, reverse engineering, or educational purposes, knowing how to leverage hexyl can greatly enhance your file analysis capabilities.