I have a Mac with snow leopard. I often work off the terminal using tmux (or GNU screen) When I walk away I remote ssh back to my computer. The thing is sometimes I have to step away from the computer for a minute or two. When that happens I don't want people to glance over and have access to my command line and I also don't think it is worth the whole CTRL-a,d,exit,open terminal, ssh to machine, tmux attach each time that happens.
Screen offered a CTRL-a,x that locked the screen (provided I enter in a password at least once that session because it won't read the system password) or in tmux (preferred) a clock feature.
All the documentation points to the fact that the multiplexers look for /usr/bin/lock or /usr/bin/lck. Since that is a low level utility found on linux and BSD systems where can I find the source so I can port it to Mac OS X?