如何在 Bash 中迭代关联数组

Posted 2023-02-14

【中文标题】如何在 Bash 中迭代关联数组

【英文标题】：How to iterate over associative arrays in Bash

【发布时间】：2011-03-07 23:05:12

【问题描述】：

基于 Bash 脚本中的关联数组，我需要对其进行迭代以获取键和值。

#!/bin/bash

declare -A array
array[foo]=bar
array[bar]=foo

我实际上不明白如何在使用 for-in 循环时获取密钥。

【问题讨论】：

$ declare -A array=( [foo]=bar [bar]=foo ) # 一次性初始化

对于一小部分键值，您可以考虑：for i in a,b c_s,d ; do KEY=$i%,*; VAL=$i#*,; echo $KEY" XX "$VAL; done

【参考方案1】：

欢迎使用输入关联数组2.0！

    clear
    echo "Welcome to input associative array 2.0! (Spaces in keys and values now supported)"
    unset array
    declare -A array
    read -p 'Enter number for array size: ' num
    for (( i=0; i < num; i++ ))
        do
            echo -n "(pair $(( $i+1 )))"
            read -p ' Enter key: ' k
            read -p '         Enter value: ' v
            echo " "
            array[$k]=$v
        done
    echo " "
    echo "The keys are: " $!array[@]
    echo "The values are: " $array[@]
    echo " "
    echo "Key <-> Value"
    echo "-------------"
    for i in "$!array[@]"; do echo $i "<->" $array[$i]; done
    echo " "
    echo "Thanks for using input associative array 2.0!"

输出：

Welcome to input associative array 2.0! (Spaces in keys and values now supported)
Enter number for array size: 4
(pair 1) Enter key: Key Number 1
         Enter value: Value#1

(pair 2) Enter key: Key Two
         Enter value: Value2

(pair 3) Enter key: Key3
         Enter value: Val3

(pair 4) Enter key: Key4
         Enter value: Value4


The keys are:  Key4 Key3 Key Number 1 Key Two
The values are:  Value4 Val3 Value#1 Value2

Key <-> Value
-------------
Key4 <-> Value4
Key3 <-> Val3
Key Number 1 <-> Value#1
Key Two <-> Value2

Thanks for using input associative array 2.0!

---

输入关联数组1.0

（不支持包含空格的键和值）

    clear
    echo "Welcome to input associative array! (written by mO extraordinaire!)"
    unset array
    declare -A array
    read -p 'Enter number for array size: ' num
    for (( i=0; i < num; i++ ))
        do
            read -p 'Enter key and value separated by a space: ' k v
            array[$k]=$v
        done
    echo " "
    echo "The keys are: " $!array[@]
    echo "The values are: " $array[@]
    echo " "
    echo "Key <-> Value"
    echo "-------------"
    for i in $!array[@]; do echo $i "<->" $array[$i]; done
    echo " "
    echo "Thanks for using input associative array!"

输出：

Welcome to input associative array! (written by mO extraordinaire!)
Enter number for array size: 10
Enter key and value separated by a space: a1 10
Enter key and value separated by a space: b2 20
Enter key and value separated by a space: c3 30
Enter key and value separated by a space: d4 40
Enter key and value separated by a space: e5 50
Enter key and value separated by a space: f6 60
Enter key and value separated by a space: g7 70
Enter key and value separated by a space: h8 80
Enter key and value separated by a space: i9 90
Enter key and value separated by a space: j10 100

The keys are:  h8 a1 j10 g7 f6 e5 d4 c3 i9 b2
The values are:  80 10 100 70 60 50 40 30 90 20

Key <-> Value
-------------
h8 <-> 80
a1 <-> 10
j10 <-> 100
g7 <-> 70
f6 <-> 60
e5 <-> 50
d4 <-> 40
c3 <-> 30
i9 <-> 90
b2 <-> 20

Thanks for using input associative array!

【参考方案2】：

declare -a arr
echo "-------------------------------------"
echo "Here another example with arr numeric"
echo "-------------------------------------"
arr=( 10 200 3000 40000 500000 60 700 8000 90000 100000 )

echo -e "\n Elements in arr are:\n $arr[0] \n $arr[1] \n $arr[2] \n $arr[3] \n $arr[4] \n $arr[5] \n $arr[6] \n $arr[7] \n $arr[8] \n $arr[9]"

echo -e " \n Total elements in arr are : $arr[*] \n"

echo -e " \n Total lenght of arr is : $#arr[@] \n"

for (( i=0; i<10; i++ ))
do      echo "The value in position $i for arr is [ $arr[i] ]"
done

for (( j=0; j<10; j++ ))
do      echo "The length in element $j is $#arr[j]"
done

for z in "$!arr[@]"
do      echo "The key ID is $z"
done
~

【参考方案3】：

使用这个高阶函数来防止pyramid of doom

foreach() 
  arr="$(declare -p $1)" ; eval "declare -A f="$arr#*=; 
  for i in $!f[@]; do $2 "$i" "$f[$i]"; done

示例：

$ bar() echo "$1 -> $2"; 
$ declare -A foo["flap"]="three four" foo["flop"]="one two"
$ foreach foo bar
flap -> three four
flop -> one two

【讨论】：

我不确定这如何适用？末日金字塔不是纯粹的美学问题，真的只适用于面向对象的语言吗？

你能解释一下吗？ foreach 函数有点棘手。我不明白。

【参考方案4】：

您可以使用$!array[@] 访问密钥：

bash-4.0$ echo "$!array[@]"
foo bar

然后，迭代键/值对很容易：

for i in "$!array[@]"
do
  echo "key :" $i
  echo "value:" $array[$i]
done

【讨论】：

我有“！” - 甚至没有注意到，没有，抱歉.. :)

【参考方案5】：

使用感叹号访问键：$!array[@]，使用$array[@] 访问值。

您可以像这样迭代键/值对：

for i in "$!array[@]"
do
  echo "key  : $i"
  echo "value: $array[$i]"
done

注意在for 语句中使用引号引起的变量（加上使用@ 而不是*）。如果任何键包含空格，这是必要的。

另一个答案的困惑来自于您的问题包括键和值的“foo”和“bar”。

【讨论】：

现在如果将所有键分配给一个数组：array=($!hash[@])

@Michael-O：你需要引用参数扩展来保护可能有空格的键：array=("$!hash[@]")

@DennisWilliamson，非常感谢。我没有这个想法。

我们如何使用函数参数编号而不是变量？例如for i in "$!$1[@]" ?

@pkaramol：从 Bash 4.3 开始，您可以使用 namerefs。示例：declare -A aa; aa['A']=a1; aa['B']=b2; aa['C']=c3; foo () declare -n assoc=$1; for key in "$!assoc[@]"; do echo "Key: $key; Value: $assoc[$key]"; done; ; foo aa。请参阅BashFAQ/006 了解一些重要信息。