Bash 使用temp变量会对数组产生不同的结果

有人能帮我解释一下在向数组中添加元素时temp变量的不同之处吗

#!/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.................................

应该是

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

应该是

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

---

你漏掉了几个括号

#!/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................................."

---

你看，在一个数组中加上arr+=（'element'），而

arr+='element'

只会在字符串中加上

arr

，你漏掉了几个括号

#!/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................................."

你看，附加到数组就像

arr+=（'element'）

，而

arr+='element'

只会附加到字符串

arr