This happens to me when I'm importing photographs, I end up with files called .JPG or .jpeg and I prefer .jpg.
for file in *.JPG
mv $file `basename $file .JPG`.jpg
The command rename does this same thing nicely, but knowing the for loop way can be more useful sometimes...and if you didn't know about rename, then I guess that would be useful too.
rename .JPG .jpg *.JPG
Say you have some files named a100 to a200 that you want to rename to b200 to b100 (it really does happen).
y=200 for x in `seq 100 200` do mv a$x b$((y--)) done
seq is a fairly useful tool, it can also take a reversed list.
for x in `seq 200 -1 100` do printf "$x " done
Copyright 2019 - All Rights Reserved