Watch output of anything in Bash
Suppose you want to keep a terminal window open showing certain processes, to watch if they’re still alive—you can pipe the output of ps into grep and then into tail:
ps -ef | grep [p]ython | tail -f
The grep pattern searches for “python” but excludes the grep command itself—I’m still not sure why, actually, but it works—at least on Linux. For some reason, OSX’s bash ignores -f for pipes, so you’d have to use a named pipe or FIFO. Handy!