I've found a serious flaw in 7zip

There is no way to enter a password on the command line automatically when decompressing. The -p flag doesn't work. Sooo, if you have a large number of files with the same password, you're screwed.

I recently found that out the hard way when I decided to mirror my online backups, or some of them, that I keep on SkyDrive on Dreamhost's backup server. The solution I came up with was to set up a temporary local telnet server and use a MUD client to automatically send the password on a periodic basis. I tried setting a trigger to send it when prompted, but the client--the free 16 bit version of Zmud running under Wine--choked on the prompt, something to due with parentheses I think. I first tried setting it to just a colon, which worked but had the tendency to create unending loops under certain conditions, and settled on the periodic sending. I really wish normal terminals had a trigger features (the ability to automatically send a command when a certain string of text is displayed) like MUD clients do. Actually, it was that thought that gave me my idea.