Creating a Hex Dump of a File

A hex dump displays the binary contents of a file in hexadecimal format, making it readable for humans. This is essential for programming, reverse engineering, data recovery, and debugging executable files. Linux provides several built-in tools to generate hex dumps of files.

To demonstrate these tools, let's first create a sample text file

$ cat > example.txt
This is our sample text in the file.
We will convert it into hex using various tools.
^D

Using hexdump Command

The hexdump command is a built-in Linux utility that displays file contents in hexadecimal, decimal, octal, or ASCII formats. It's particularly useful for inspecting executable code and data recovery.

Basic Syntax

$ hexdump [options] [files]

Default Hex Output

By default, hexdump displays data as 16-bit hexadecimal numbers

$ hexdump example.txt

0000000 6854 7369 6920 2073 756f 2072 6173 706d
0000010 656c 7420 7865 2074 6e69 7420 6568 6620
0000020 6c69 2e65 570a 2065 6977 6c6c 6320 6e6f
0000030 6576 7472 6920 2074 6e69 6f74 6820 7865
0000040 7520 6973 676e 7620 7261 6f69 7375 7420
0000050 6f6f 736c 0a2e
0000056

Canonical Format with ASCII

Use the -C flag to display both hex and ASCII data side by side

$ hexdump -C example.txt

00000000  54 68 69 73 20 69 73 20  6f 75 72 20 73 61 6d 70  |This is our samp|
00000010  6c 65 20 74 65 78 74 20  69 6e 20 74 68 65 20 66  |le text in the f|
00000020  69 6c 65 2e 0a 57 65 20  77 69 6c 6c 20 63 6f 6e  |ile..We will con|
00000030  76 65 72 74 20 69 74 20  69 6e 74 6f 20 68 65 78  |vert it into hex|
00000040  20 75 73 69 6e 67 20 76  61 72 69 6f 75 73 20 74  | using various t|
00000050  6f 6f 6c 73 2e 0a                                 |ools..|
00000056

Using xxd Command

The xxd utility creates hex dumps and can also reverse hex dumps back to their original binary format. It provides a clean, readable output format.

Syntax

$ xxd [options] [file]

Example

$ xxd example.txt

00000000: 5468 6973 2069 7320 6f75 7220 7361 6d70  This is our samp
00000010: 6c65 2074 6578 7420 696e 2074 6865 2066  le text in the f
00000020: 696c 652e 0a57 6520 7769 6c6c 2063 6f6e  ile..We will con
00000030: 7665 7274 2069 7420 696e 746f 2068 6578  vert it into hex
00000040: 2075 7369 6e67 2076 6172 696f 7573 2074   using various t
00000050: 6f6f 6c73 2e0a                             ools..

Using od Command

The od (octal dump) command converts files to different formats. While it defaults to octal format, we can specify hexadecimal output using the -t x1 flag.

Hexadecimal Output

$ od -t x1 example.txt

0000000 54 68 69 73 20 69 73 20 6f 75 72 20 73 61 6d 70
0000020 6c 65 20 74 65 78 74 20 69 6e 20 74 68 65 20 66
0000040 69 6c 65 2e 0a 57 65 20 77 69 6c 6c 20 63 6f 6e
0000060 76 65 72 74 20 69 74 20 69 6e 74 6f 20 68 65 78
0000100 20 75 73 69 6e 67 20 76 61 72 69 6f 75 73 20 74
0000120 6f 6f 6c 73 2e 0a
0000126

Combined Hex and Character Display

Combine -t x1 and -c flags to show both hex values and character representation

$ od -t x1 -c example.txt

0000000 54 68 69 73 20 69 73 20 6f 75 72 20 73 61 6d 70
   T   h   i   s       i   s       o   u   r       s   a   m   p
0000020 6c 65 20 74 65 78 74 20 69 6e 20 74 68 65 20 66
   l   e       t   e   x   t       i   n       t   h   e       f
0000040 69 6c 65 2e 0a 57 65 20 77 69 6c 6c 20 63 6f 6e
   i   l   e   .  
   W   e       w   i   l   l       c   o   n
0000060 76 65 72 74 20 69 74 20 69 6e 74 6f 20 68 65 78
   v   e   r   t       i   t       i   n   t   o       h   e   x
0000100 20 75 73 69 6e 67 20 76 61 72 69 6f 75 73 20 74
       u   s   i   n   g       v   a   r   i   o   u   s       t
0000120 6f 6f 6c 73 2e 0a
   o   o   l   s   .  

0000126

Comparison of Tools

Conclusion

Linux provides multiple tools for creating hex dumps, each with unique advantages. The hexdump command offers versatile formatting options, xxd provides clean readable output with reversibility, and od excels at multiple format conversions. These tools are essential for debugging, reverse engineering, and analyzing binary file contents.