sed is such a useful pattern-matching and substitution tool for work on the command line. But there’s a little quirk on macOS that will trip you up. It tripped me up. On most platforms, \s is the character class for whitespace. It’s ubiquitous in regexes. But on macOS, it doesn’t work. In fact, it silently fails. Consider this bash one-liner which looks like it should work but doesn’t: # should print I am corrupt (W.