f3read man page
f3write, f3read — test real flash memory capacity
f3write [--start-at=NUM] [--end-at=NUM] <PATH> f3read [--start-at=NUM] [--end-at=NUM] <PATH>
F3 (Fight Flash Fraud or Fight Fake Flash) tests the full capacity of a flash card (flash drive, flash disk, pendrive). It writes to the card and then checks if can read it. It will assure you haven't been sold a card with a smaller capacity than stated.
When writing to flash drive, f3write fills the filesystem with 1GB files named N.h2w, where N is a number (i.e. /[0-9]+/).
WARNING: all data on the tested disk might be lost!
Initial number of file names. Default value is 1.
Final number of file names. Default value is "infinity".
To write over a flash drive mounted at /media/TEST:
$ f3write /media/TEST
To read this flash drive:
$ f3read /media/TEST
F3 was written by Michel Machado <firstname.lastname@example.org>. This manual page was first written by Joao Eriberto Mota Filho <email@example.com>.