Bash for 循环获取上一项和下一项
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Bash for loop get previous and next item
提问by Guillaume
I would like to do a loop and inside the loop get the previous and the next item.
我想做一个循环并在循环内获取上一个和下一个项目。
Currently, I am using the following loop:
目前，我正在使用以下循环：
for file in $dir;do
[...do some things...]
done
Can I do things like in C, for example, file[i-1]/file[i+1] to get the previous and the next item? Is there any simple method to do this?
我可以在 C 中做一些事情，例如，file[i-1]/file[i+1] 来获取上一个和下一个项目吗？有没有什么简单的方法可以做到这一点？
回答by Vivek
declare -a files=(*)
for (( i = 0; i < ${#files[*]}; ++ i ))
do
echo ${files[$i-1]} ${files[$i]} ${files[$i+1]}
done
In the first iteration, the index -1 will print the last element and in the last iteration, the index max+1 will not print anything.
在第一次迭代中，索引 -1 将打印最后一个元素，在最后一次迭代中，索引 max+1 将不打印任何内容。
回答by Pavel Strakhov
Try this:
尝试这个：
previous=
current=
for file in *; do
previous=$current
current=$next
next=$file
echo $previous \| $current \| $next
#process item
done
previous=$current
current=$next
next=
echo $previous \| $current \| $next
#process last item
