I don't really think it's fair to call anything that's in a POSIX standard obscure (like xargs).
Most of these are fairly common, and many of the descriptions are terrible, for example: `rsync` doesn't "[Keep] filesystems in sync over SSH"; it's a versatile `cp`-like for dealing with remote systems efficiently that happens to support transfers over SSH.
Most of these are fairly common, and many of the descriptions are terrible, for example: `rsync` doesn't "[Keep] filesystems in sync over SSH"; it's a versatile `cp`-like for dealing with remote systems efficiently that happens to support transfers over SSH.