为何shellfor循环列表不能成功解析xargs中的变量呢？

for i in {1..3,7..9}; do for j in {$i}; do echo -n "$j,"; done; done

1,2,3,7,8,9

# 替换-为..

echo "1-3,7-9" | sed 's/-/../g'

1..3,7..9

# 确定能够正确识别@

echo "1-3,7-9" | sed 's/-/../g' | xargs -I@ echo @

1..3,7..9

# 将@变量放到for中 报错

echo "1-3,7-9" | sed 's/-/../g' | xargs -I@ for i in {@}; do for j in {$i}; do echo -n "$j,"; done; done

zsh: parse error near `do'