Need to create zero-filled files to test things?
Have a Mac?
The mkfile command is your friend.

Syntax: mkfile -n size[b|k|m|g] filename

Examples of usage in Terminal (note these will place the files on your Mac desktop):
mkfile -n 10m ~/Desktop/10megfile
mkfile -n 15m ~/Desktop/15megfile
mkfile -n 16m ~/Desktop/16megfile
mkfile -n 17m ~/Desktop/17megfile
mkfile -n 18m ~/Desktop/18megfile
mkfile -n 19m ~/Desktop/19megfile
mkfile -n 20m ~/Desktop/20megfile
mkfile -n 25m ~/Desktop/25megfile

These could be used for testing the permitted size of email attachments, for example.

Note that the output of the above commands is available for download as a .ZIP file from our website here