问Bash嵌套循环行为

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file=`cat files.txt`

# read the lines in the file and store every line in variable as "line"
while read -r line; do
# declare an array variable from every space separated value in "line"
  declare -a arr=`echo $line`
# set counter to zero
  num=0
# now loop through the above array
  for i in ${arr[*]}; do
# set a variable as "a_$num" that equals the current value in array
  eval a_${num}="'\"$(echo $i)\"'"
# incremenate "num" by 1 
  ((num=num+1))
  done
# echo the first value in current line
  echo $a_0
done <<< $file

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