In linux, what would happen to a running program when it's executable file has been modified or deleted?
It depends on exactly how the executable is updated. If the same file is opened and parts of it are changed, bad things will happen. If it is removed, the file is removed from the directory structure of the filesystem, but not actually unlinked (i.e., deleted) until the last process that has it open has executed it exits. So if the executable is removed and a new one with the same name written in its place, the old one should continue to work ok.
They'll keep on going. Maybe crash horribly if they try and access themselves and receive something utterly wrong. I wouldn't do it unless I had to :)
What will happen to those running ruby processes?
- make a copy of /usr/local/bin/ruby
- [if it's not running, run /usr/local/bin/ruby ]
- try: rm /usr/local/bin/ruby
- and see for yourself :)