索引数组：1到数组的长度

Question

对不起， 标题不好，请随时将其调整为更合适的名称。

我如何使用zsh或bash脚本为数组建立索引，就像我在下面的R中为列表所做的那样；

# Some lists with the same number of elements
list1 <- list(sample(letters,10))
list2 <- list(1:10)

for(i in 1:length(list1)) {
  a <- list1[[1]][i]
  b <- list2[[1]][i]
}

print(paste(a,b))  # Or some other function where a and b are used simultaneously

[1] "f 1"
[1] "e 2"
[1] "t 3"
[1] "s 4"
[1] "c 5"
[1] "o 6"
[1] "p 7"
[1] "y 8"
[1] "k 9"
[1] "d 10"

下面的代码显然只打印两个列表中的最后一个元素，因为我还没有找到对数组长度做1的方法

# dummy data

echo 'A 1' > A.txt
echo 'B 1' > B.txt
echo 'C 1' > C.txt

echo 'A,2' > A.csv
echo 'B,2' > B.csv
echo 'C,2' > C.csv

txtlist=(*.txt) # create an array of .txt files
csvlist=(*.csv) # create an array of .csv files

# in zsh $#array returns the length of the array, so 

for i in $#txtlist; do
    a=$txtlist[i]
    b=$csvlist[i]

    echo $a,$b  # Or some other function where a and b are used simultaneously

done

#C.txt,C.csv

任何指针将不胜感激，谢谢！

Answer 1

bash和zsh都知道C样式的for循环：

从man 1 zshmisc （ man 1 bash本质上是相同的）：

for (( [expr1] ; [expr2] ; [expr3] )) do list done
       The  arithmetic expression expr1 is evaluated first (see the section `Arithmetic Evaluation').  The arithmetic expression expr2 is repeatedly
       evaluated until it evaluates to zero and when non-zero, list is executed and the arithmetic expression expr3 evaluated.  If any expression is
       omitted, then it behaves as if it evaluated to 1.

zsh示例：

for (( i=1; i<=$#txtlist; i++ )); do
    echo "$txtlist[$i]" "$csvlist[$i]"
done

bash示例：

for (( i=0; i<=${#txtlist[@]}; i++ )); do
    echo "${txtlist[$i]}" "${csvlist[$i]}"
done

Answer 2

很抱歉，我不确定您是否理解您的示例，但是，您可以在bash中执行类似的循环：

myLength=${#myArray[@]}
for (( i=1; i<${myLength}; i++ ));
do
  echo ${myArray[$i]}
done

Answer 3

使用以下语法：

$ x=(1 2 3 4 5)
$ print $x
1 2 3 4 5
$ print ${x:1}
2 3 4 5