Geekblok

This trick is a bit bash specific instead of a real shell trick. On most unix systems you’ll find the commands dirname and basename. These are rather useless when you have got bash. First we’ll look at dirname.
The manual page of dirname states: dirname - strip non-directory suffix from file name. In bash this would be accomplished by parameter expansion:

$ I=/home/joffie/geekblok.txt; echo ${I%/*}
/home/joffie

The description from the man page of basename is: strip directory and suffix from filenames. So for example:

$ basename /home/joffie/geekblok.txt
geekblok.txt

The same can be accomplished with:

$ I=/home/joffie/geekblok.txt; echo ${I##*/}
geekblok.txt

The suffix part of the basename command can be done in two steps. What the command basename does is strip something from both sides of the string. So stripping suffix .txt from $I too:

$ I=/home/joffie/geekblok.txt; J=${I##*/}; echo ${J%.txt}
geekblok

Bash can also be used when searching and replacing. Take a look at:

$ I=/home/joffie/geekblok.txt; echo ${I/geek/cool}
coolblok.txt

More info can be found in the parameter expansion section of the man page of bash.