Quick Tip: delete line with sed

Running a bunch of vulnhub vms frequently, I’ve found a need to quickly delete a line from my ~/.ssh/known_hosts file. So I learned this:

$ sed -i ‘’ ‘/pattern/d’ filename.ext

This edits in place a given <filename.ext>, dropping any lines that match the <pattern>. Took me about 20 minutes to figure out that an eccentricity in the BSD version of sed requires the extra empty quotes. Originally I was trying the following, which should work on Linux, but not OS X.

$ sed -i '/' ./known_hosts
sed: 1: "./known_hosts": invalid command code .

I found the solution in the comments of a stack overflow answer. I’m sure there’s a good reason it works differently in BSD vs GNU, but it’s not worth my time to learn why at this particular moment.