Paths — basename, dirname, realpath

Each of the three utilities has its own small set of options. basename -s strips a suffix without a separate sed call, -a takes several paths at once. realpath -e requires the whole path to actually exist, while -m does the opposite — it computes the path as a plain string even if the file doesn't exist yet; confusing the two is a common source of bugs in scripts that prepare a path for a file they're about to create themselves.