In my experience, most computational chemists only know a handful of basic Bash commands, which is a shame because Bash is incredibly powerful. Although I'm far from an expert, here are a few commands I frequently find myself using: 1. sed For Find-and-Replace. $ sed -i “s/b3lyp/m062x/” *.gjf If you want to resubmit a bunch of transition states at a different level of theory, don't use a complex package like cctk!