This is sometimes useful when playing with bigdata.
Instead of a dd command and wait the file being created block by clock, we can run:
$ fallocate -l 200G /mnt/reallyBigFile.csv
It essentially “allocates” all of the space you’re seeking, but it doesn’t bother to write anything. So, when you use fallocate to create a 200 GB virtual drive space, you really do get a 200 GB file.