random-fill is a simple tool to fill random data into a file to overwrite the free space on a disk,
it works like macOS diskutil secureErase freespace or Linux sfill in secure-delete package.
If you want to wipe your whole disk, please use diskutil secureErase (without freespace option) or shred.
Keep in mind, random-fill is not exactly the same as these tools. random-fill is working for a speed purpose:
it will write as fast as it can and the random data may be re-used during filling.
random-fill uses a big random data pool to provide random data.
The file is filled by the data from the random data pool.
The slower your CPU/CSPRNG is, the more times the random data will be used.
$ random-fill
Usage: ./random-fill {count} {file} [size]
(the [size] is for development purpose, it shouldn't be used by end users)
$ random-fill 2 /tmp/test.dat 1000000000
2021/12/30 11:35:27 fill 2 times to file: /tmp/test.dat, disk avail=353.95 GiB
2021/12/30 11:35:27 fill up to 953.67 MiB bytes
2021/12/30 11:35:27 fill step 1, write to /tmp/test.dat
step: 1, speed: 621.42 MiB/s (written: 926.97 MiB) ...
2021/12/30 11:35:29 fill step 1 written 953.68 MiB bytes to /tmp/test.dat
2021/12/30 11:35:29 fill step 1 removes file /tmp/test.dat
2021/12/30 11:35:29 fill step 2, write to /tmp/test.dat
step: 2, speed: 570.97 MiB/s (written: 890.41 MiB) ...
2021/12/30 11:35:31 fill step 2 written 953.68 MiB bytes to /tmp/test.dat
2021/12/30 11:35:31 fill step 2 (final) keeps file /tmp/test.dat