hexdump Command in Linux

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hexdump is a robust command-line utility in Linux that converts the contents of a file into a readable format. It supports multiple formats, such as −

• Hexadecimal − Base-16 representation
• ASCII − Character representation
• Octal − Base-8 representation
• Decimal − Base-10 representation

Developers often deal with binary data, which is not easily readable. Converting this data into a format that humans can understand (like hexadecimal or ASCII) makes it easier to analyze and debug.

• The hexdump command-line utility is commonly used by professionals who need to inspect and analyze binary data, such as programmers and system administrators.
• hexdump is versatile and can be used in various scenarios, such as inspecting the contents of files stored on disk, reading and analyzing the structure of disk partitions or filesystems.
• In addition, you can also use this hexdump to analyze data captured from network traffic or serial communication and examine memory dumps' contents for debugging or forensic purposes.
• To use hexdump, you need to provide a file or standard input. The command will then convert the input data into the specified format.
• Other commands like xxd and od can also convert binary data into readable formats. These tools offer similar functionality and can be used as alternatives to hexdump.
• hexdump is typically included by default in most Linux distributions. On Ubuntu, it is part of the bsdmainutils

Table of Contents

Here is a comprehensive guide to the options available with the hexdump command −

• Syntax for the hexdump Command
• Options Available for the hexdump Command
• Examples of hexdum Command in Linux

Syntax for the hexdump Command

The following is the basic syntax for the hexdump command −

hexdump [OPTIONS] [FILE]

Options Available for the hexdump Command

The following is a list of options alongside their descriptions for hexdump or hd commands −

Examples of hexdum Command in Linux

In this section, we'll explore various examples that should help you get started with using the hexdump command −

Basic Hex Dump

To display the contents of a file in a hexadecimal format, you can simply run the following command −

hexdump samplefile.txt

This command outputs the contents of samplefile.txt in hexadecimal format.

Where −

• The first column shows the offset in the file.
• The subsequent columns display the hexadecimal representation of the file's contents.

One-byte Octal Display

You can use the "-b" option with the hexdump command to display a file's contents in a one-byte octal format. This is useful for examining the raw data in a file byte by byte.

To achieve this, you can simply run the following command −

hexdump -b samplefile.txt

This command outputs each byte of samplefile.txt in octal format.

In this output −

• The first column shows the offset in the file.
• The subsequent columns display the octal representation of each byte in the file.

One-byte Character Display

You can use the hexdump command with the "-c" flag to display the contents of a file in a one-byte character format. This means each byte is shown as an ASCII character, which is useful for visualizing text data.

hexdump -c samplefile.txt

This command outputs each byte of samplefile.txt as an ASCII character.

In this output −

• The first column shows the offset in the file.
• The subsequent columns display the ASCII representation of each byte in the file.

Two-byte Decimal Display

To display the contents of a file in a two-byte decimal format, you can use the "-d" option with the hexdump command −

hexdump -d samplefile.txt

This is useful for examining data in a more human-readable numeric form. This command outputs each two-byte chunk of samplefile.txt in decimal format.

In this output −

• The first column shows the offset in the file.
• The subsequent columns display the decimal representation of each two-byte chunk in the file.

Limit Output Length

You can use the "-n" option with the hexdump command to limit the output to a specified number of bytes. This can be useful when you only need to inspect a small portion of a file.

hexdump -n 16 samplefile.txt

This command outputs the first 16 bytes of samplefile.txt.

In this output −

• The first column shows the offset in the file.
• The subsequent columns display the hexadecimal representation of the first 16 bytes.

Skip Bytes

To skip a specified number of bytes from the beginning of the file before starting the dump, you can simply use the "-s" option with the hexdump command −

hexdump -s 10 samplefile.txt

This command skips the first 10 bytes of samplefile.txt and then displays the hexadecimal representation of the remaining content.

Two-byte Hexadecimal Display

To display the file content in two-byte hexadecimal format, you run the following command −

hexdump -x samplefile.txt

This command outputs the contents of samplefile.txt in hexadecimal, grouping the data into two-byte (16-bit) words.

Specify Format String

To specify a custom format string for the output, you can use the "-e" flag with the hexdump command −

hexdump -e '16/1 "%02x "' samplefile.txt

This command displays the contents of samplefile.txt in a specific format:

In this command −

• 16/1 means to display 16 bytes per line, with each byte being processed individually.
• "%02x" specifies the format for each byte: a two-digit hexadecimal number (%02x) followed by a space.

Conclusion

The hexdump command in Linux is an invaluable tool for anyone working with binary data, offering a straightforward way to visualize file contents in various formats such as hexadecimal, ASCII, and more.

Whether you're examining disk partitions, analyzing network traffic, or debugging memory dumps, mastering the hexdump command can significantly streamline your workflow.