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How to Create a File of Any Size on Linux and Windows

In Linux, the dd command is commonly used to test disk I/O by generating files of specific sizes. When working on Windows, you might wonder if there's a similar approach. The good news is, Windows provides a built-in command to create files of arbitrary sizes using fsutil, available since Windows XP.

Creating Files on Windows

The fsutil command allows you to create a file of any size with a simple syntax:

fsutil file createnew <filename> <size>

Here, <size> is specified in bytes (B). For example, to create a 500 MB (500 × 1024 × 1024) file:

fsutil file createnew 500MB.zip 524288000

Understanding the File Content

If you open the generated file in a text editor like Notepad, the content will appear empty. This is because the file consists of binary zeroes, which correspond to empty space in ASCII. However, if you open it in a hex editor like UltraEdit, you'll see its binary representation:

00000000h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ; ................
00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ; ................
00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ; ................

This shows that the file is filled entirely with binary zeroes.

Creating Files on Linux

On Linux, the equivalent of the fsutil command is dd, a versatile tool used for creating files, copying data, and more. To generate a 500 MB file, use the following command:

dd if=/dev/zero of=500MB.zip bs=1M count=500

Explanation of Parameters

  • if=/dev/zero: Input file. /dev/zero is a special file that generates null bytes.
  • of=500MB.zip: Output file.
  • bs=1M: Block size, set to 1 MB.
  • count=500: Number of blocks to write, resulting in 500 MB.

Practical Use Cases

  • Disk I/O Testing: Both commands are commonly used to benchmark or test the performance of storage systems.
  • File Size Simulation: Creating dummy files for testing applications that handle large data files.

References

  1. Using Fsutil Command to Manage and Repair File Systems in Windows

Both fsutil and dd are efficient tools for generating files of arbitrary sizes on their respective platforms. Choose the one that fits your operating system and requirements!

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