Bash

Question

在 Bash 中有没有办法使指针指向 [=35] 中键的值 =]关联数组？像这样：

declare -A mapp
mapp=( ["key"]="${value}" )

for k in "${!mapp[@]}"; do 
    pointer="${mapp["${k}"]}"   # How do I do this?
done

通常，您不需要使用指针，但我很想知道是否有办法制作指针。

在更简单的情况下（即，对于 normal/string 变量），我会像这样创建一个指针：

pointer=b
read -p "Enter something: " b
eval pointer=$${pointer}

如何为关联数组执行此操作？这不起作用（跳过带删除线的代码）：

~~declare -A mapp mapp=( ["first"]="${a}" ["second"]="${b}" ) for k in "${!mapp[@]}"; do v=mapp["${k}"] read -p "Enter ${k}: " new eval v=$${v} # Doesn't work done~~

declare -A mapp
mapp=( ["first"]="${a}"  ["second"]="${b}" )

for k in "${!mapp[@]}"; do 
    v=mapp["${k}"]

    read -p "Enter ${k}: " k

    eval v=$${v}    # Doesn't work

done

这也不起作用（跳过带删除线的代码）：

~~declare -A mapp mapp=( ["first"]="${a}" ["second"]="${b}" ) for k in "${!mapp[@]}"; do v=mapp read -p "Enter ${k}: " new eval v=$${v["${k}"]} # Doesn't work (and has terrible readability) done~~

declare -A mapp
mapp=( ["first"]="${a}"  ["second"]="${b}" )

for k in "${!mapp[@]}"; do 
    v=mapp

    read -p "Enter ${k}: " k

    eval v=$${v["${k}"]}    # Doesn't work (and has terrible readability)

done

Answer 1

没问题：

$ declare -A ary=([foo]=bar [baz]=qux)
$ key=foo
$ pointer="ary[$key]"
$ echo "$pointer"
ary[foo]
$ echo "${!pointer}"
bar

A "pointer" 在这个意义上是 indirect variable

Answer 2

在 bash 4.3 中，您可以使用 nameref:

$ mapp=([key]=value)
$ declare -n x=mapp[key]  # NO dollar sign!
$ x=7
$ echo ${mapp[key]}
7

在 4.3 之前，您需要使用不同的 declare 命令来进行间接寻址。

$ mapp=([key]=value)
$ x=mapp[key]  # NO dollar sign!
$ declare "$x=7"
$ echo ${mapp[key]}
7

Bash - 指向关联数组中值的指针？

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