files=(a b c d e f g h i j k l m n o p)

cnt="${#files[@]}"

let cnt1="($cnt+2)/3"

let cnt2="$cnt1*2"

let cnt3="$cnt-$cnt2"

files_part1=( "${files[@]:0:$cnt1}" )

files_part2=( "${files[@]:$cnt1:$cnt1}" )

files_part3=( "${files[@]:$cnt2:$cnt3}" )

printf '%s\n' "${files_part1[@]}"

echo "xxxxxxxxxxxxxx"

printf '%s\n' "${files_part2[@]}"

echo "xxxxxxxxxxxxxx"

printf '%s\n' "${files_part3[@]}"

#for each in "${files[@]}"; do  #echo "$each"#done

 结果：

**************

a

b

c

d

e

f

xxxxxxxxxxxxxx

g

h

i

j

k

l

xxxxxxxxxxxxxx

m

n

o

p