It is good example that argv[0] is just another normal argument that is passed by the caller of execve() and does not necessarily have to be related to the actual filename of program executed in any way.
Not sure if it still works that way, but years ago I used to overwrite the argv[0] param with my own data to change how the process appears on lists such as one shown by the 'w' utility.
Yep. There's a tool in djb's daemontools that uses this behavior - https://cr.yp.to/daemontools/readproctitle.html . It's kinda a pathological case, but it's a kinda cool way to assure that you can get some data from your processes, even on a totally horked system, as well as being fairly convenient from an old-school administration perspective (giving the ability to see what errors a program has encountered with just ps or top; Already likely to be the first commands run when something's wrong.)
