How to quickly generate test files of a specified size? It can be achieved using command line tools or graphical software. On Windows, you can use fsutil file createnew file size to generate a file with a specified byte; macOS/Linux can use dd if=/dev/zero of=file bs=1M count=100 to generate real data files, or use truncate -s 100M file to quickly create sparse files. If you are not familiar with the command line, you can choose FSUtil GUI, Dummy File Generator and other tool software. Notes include: paying attention to file system limitations (such as FAT32 file size upper limit), avoiding overwriting existing files, and some programs may not recognize sparse files. The above methods are suitable for speed measurement, stress test and other scenarios, and you can choose as needed.

Sometimes you need a file of a specific size to do the test, such as speed measurement, stress testing, storage occupancy simulation, etc. At this time, it is the most direct way to generate a file of the specified size by yourself.

Quickly generate fixed-size files using the command line

Both Windows and macOS/Linux can quickly create empty files and specify sizes through the command line, without really writing large amounts of data, fast and suitable for large files.

• On Windows, you can use the fsutil command:

 fsutil file createnew testfile.txt 104857600

The above command will create a file named testfile.txt , with a size of 100MB (units in bytes).

• You can use dd or truncate on macOS or Linux :

 dd if=/dev/zero of=testfile.bin bs=1M count=100

This command will generate a 100MB binary file. bs=1M means 1MB is written each time, count=100 means 100 times.

If you want to be faster but don't need real data content, you can use:

 truncate -s 100M testfile.empty

This method generates "sparse files", which look like they are of size, but actually does not occupy full disk space.

More intuitive operation with tool software

If you are not familiar with the command line, you can also use some graphical tools to generate files of a specified size.

• FSUtil GUI (Windows): It is an encapsulation of native commands and has an interface-friendly.
• Dummy File Generator (cross-platform): supports selection of file size, format and path, suitable for those who do not want to type commands.
• On a Mac, you can also use terminals to cooperate with scripts to automatically generate multiple test files of different sizes.

The advantage of this type of tool is that it does not require commands, but the disadvantage is that it requires additional installation and is suitable for single-use or non-technical personnel.

Notes and FAQs

• File system limitations : Some file systems (such as FAT32) have restrictions on a single file size, which may not be generated beyond the limit.
• Do not misoperate and overwrite existing files : pay attention to whether the file name is duplicated when executing the command to avoid overwriting the original data.
• Sparse files are not supported by all systems : some programs may consider it blank or corrupt when reading sparse files.

If it is just used to test upload, download speed or capacity occupancy, these methods can basically meet the needs.

Basically all that is it, just choose the most convenient way for you.

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