for

for ((init; cond; incr))
do
    commands
done

ksh93 only. Arithmetic for loop, similar to C's. Evaluate init. While cond is true, execute the body of the loop. Evaluate incr before re-testing cond. Any one of the expressions may be omitted; a missing cond is treated as being true.

Examples

Search for a phrase in each odd chapter:

for ((x=1; x <= 20; x += 2))
do
	grep $1 chap$x
done