尝试递增关联数组元素时出现错误的数组下标错误 [英] Bad array subscript error when trying to increment an associative array element

问题描述

我可以创建一个关联数组，并为其中包含单引号的键分配一个整数:

I can create an associative array and assign an integer to a key that contains a single quote in it:

$ declare -A dict
$ var="john's"
$ dict[$var]=1
$ echo ${dict[$var]}
1
$ declare -p dict
declare -A dict=(["john's"]="1" )

但是当我尝试增加其值时:

But when I try to increment its value:

$ (( dict[$var]++ ))
bash: ((: dict[john's]++ : bad array subscript (error token is "dict[john's]++ ")
$ (( dict["$var"]++ ))
bash: ((: dict[john's]++ : bad array subscript (error token is "dict[john's]++ ")
$ (( dict["${var}"]++ ))
bash: ((: dict[john's]++ : bad array subscript (error token is "dict[john's]++ ")

我总是遇到相同的错误.我在做什么错了?

I always get the same error. What am I doing wrong?

推荐答案

key名称中的单引号使解析器将其视为未终止的引号字符.解决此问题的一种方法是转义键中的'字符

The single quote in key name is causing the parser to treat it as a un-terminated quote character. One way to fix this would be to escape the ' character in the key

key="john's"
printf -v escKey "%q" "$key"

现在由于%q指示符， printf() 会将必需的转义符应用于所有shell元字符，即使其成为"shell引用"且可重复使用.如果打印escKey的内容，您会发现'转义了

now because of the %q specifier, printf() would have applied required escapes to all shell meta characters i.e. making it "shell-quoted" and re-usable. If you print the contents of escKey you'll notice the ' escaped

printf '%s\n' "$escKey"
john\'s

现在，您可以在关联数组中使用此键名.请记住，您始终可以手动添加可能会造成混乱的转义符.由于%q是Shell提供的一种本机方式，因此使用它非常安全.

Now you can use this keyname in your associative array. Remember you can always manually add the escapes which could be messy. Since %q is a native way provided by the shell, it is much safe to use it.

(( dict["$escKey"]++ ))

也为bash版本> = 4.4 参数扩展具有@Q，这是printf()的%q指定符的快捷方式，您可以使用

Also in bash versions >= 4.4 parameter expansion has @Q which is a shortcut for %q specifier of printf() using which you can do

(( dict["${key@Q}"]++ ))

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