Question

有人可以帮我解释临时变量的差异，因为我正在向数组中添加元素吗？

#!/bin/bash

declare -a finaldirs1
declare -a finaldirs2

declare -a files=("Planes" "Trains" "Automobiles")

echo "A)..................................."
for el1 in "${files[@]}"; do
    tmpe=$(printf "1:%s." "${el1}")
    finaldirs1+=($tmpe)
done
for elA in "${finaldirs1[@]}"; do
    echo "First: " $elA
done

echo "B)..................................."
for el2 in "${files[@]}"; do
    finaldirs2+=$(printf "2:%s." "${el2}")
done
for elB in "${finaldirs2[@]}"; do
    echo "Second: " $elB
done
echo "DONE................................."

简而言之，第二个版本以某种方式将所有元素组合在一起。输出：

A)...................................
First:  1:Planes.
First:  1:Trains.
First:  1:Automobiles.
B)...................................
Second:  2:Planes.2:Trains.2:Automobiles.
DONE.................................

Answer 1

finaldirs2+=$(printf "2:%s." "${el2}")

应该是

finaldirs2+=($(printf "2:%s." "${el2}"))

Answer 2

你错过了几个括号。

#!/bin/bash

declare -a finaldirs1
declare -a finaldirs2

declare -a files=("Planes" "Trains" "Automobiles")

echo "A)..................................."
for el1 in "${files[@]}"; do
    tmpe=$(printf "1:%s." "${el1}")
    finaldirs1+=($tmpe)
done
for elA in "${finaldirs1[@]}"; do
    echo "First: " $elA
done

echo "B)..................................."
for el2 in "${files[@]}"; do
    finaldirs2+=($(printf "2:%s." "${el2}"))
done
for elB in "${finaldirs2[@]}"; do
    echo "Second: " $elB
done
echo "DONE................................."

您可以看到，附加到数组时它就像arr+=('element')一样，而arr+='element'只会附加到字符串arr。

使用temp变量会产生与数组不同的结果

2 个答案: