Don’t write for loops in shell scripts.  They are one reason they get
a reputation for being annoying to write, difficult to follow, and a
lower-class programming language.¹  Instead, separate the bodies of
for loops into their own reusable, parameterized functions or files.
Then, apply the function or call the script file over a set of data
with functional programming primitives² such as map, reduce or folds,
filter, et cetera.  This project provides implementations of these
primitives, as scripts and functions, for various shells.
 ¹ Lack of types—or, everything is one type—is another, but that
hasn't seemed to much hurt Lisps.
 ² Introductory justification with examples: Spolsky, J.  20060801.
Can your programming language do this?  Joel on software.
http://www.joelonsoftware.com/items/2006/08/01.html