Shell 005: String processing

A directory contains the following

~/shell $ ls -l
00_01_boxpdb.py
00_01_realign.py
00_02_callPDB2PQR.py
00_03_getPointCharges.py
00_04_getCharge.py
01_01_connect.py

How can the leading terms be removed?

~/shell $ for i in 0*
> do
> mv $i ${i:6}
> done

The syntax is ${i:FROM:BY}. The indexing starts from 0. Also

# Is it possible to index from the right end of the string?
    
echo ${stringZ:-4}               # abcABC123ABCabc
# Defaults to full string, as in ${parameter:-default}.
# However . . .

echo ${stringZ:(-4)}             # Cabc 
echo ${stringZ: -4}              # Cabc
# Now, it works.
# Parentheses or added space "escape" the position parameter.