mv foo/bar/poit/zoid/narf.txt

mv foo/bar/poit/zoid/narf.txt foo/bar/poit/zoid/troz.txt

mv foo/bar/poit/zoid/{narf.txt,troz.txt}

mv foo/bar/poit/zoid/{narf,troz}.txt

mv foo/bar/poit/zoid/narf.txt

mv path/you/do/not/want/to/type/twice/oldname !#$:h/newname

a=test.csv ; cp $a $a.bak

a=foo/bar/poit/zoid/ ; mv ${a}narf.txt ${a}troz.txt