英文:
Link variables in GNU Bash (4.4.20)
问题
在GNU Bash（版本5.0.17）中，我想要链接两个（或更多）变量，即当变量#1的值发生变化时，变量#2应自动设置为变量#1的值，反之亦然。
我尝试了以下方法（都是在Bash命令行中），它可以工作，但只有在在变量名后插入一个空格时才有效。然而，这对我来说不够好，我更希望myvar1=test，即没有空格，但我担心这可能不可能...？
$ bash --version
> GNU bash, version 5.0.17(1)-release
$ myvar1() {
myvar1=$(echo "$@" | cut -d'=' -f2-)
myvar2="$myvar1"
}
$ myvar2() {
myvar1=$(echo "$@" | cut -d'=' -f2-)
myvar2="$myvar1"
}
$ echo "$myvar1:$myvar2:" # 此时未设置
> ::
$ myvar1=abc
$ echo "$myvar1:$myvar2:"
> abc:abc:
$ myvar2=def
$ echo "$myvar1:$myvar2:"
> def:def:
这样做的原因是为了保持旧变量仍然在使用，同时支持在其他地方使用的新变量，这些变量对值应该保持一致。
英文:
In GNU Bash (5.0.17) I would like to link two (or more) variables i.e., when variable #1 changes value, variable #2 should automatically have its value set to the value of variable #1 and vice versa.
I've tried the following (all from Bash command line), and it works, but only when you insert a space after the variable name during assignment.
However this not good enough for me, I'd prefer myvar1=test i.e. without space, but I fear this is not possible...?
$ bash --version
> GNU bash, version 5.0.17(1)-release
$ myvar1() {
myvar1=$(echo "$@" | cut -d'=' -f2-)
myvar2="$myvar1"
}
$ myvar2() {
myvar1=$(echo "$@" | cut -d'=' -f2-)
myvar2="$myvar1"
}
$ echo "$myvar1:$myvar2:" # Unset at this point
> ::
$ myvar1 =abc
$ echo "$myvar1:$myvar2:"
> abc:abc:
$ myvar2 =def
$ echo "$myvar1:$myvar2:"
> def:def:
The reason for this is to keep legacy variables still being used but also support new variables, used elsewhere, where these variable pairs should go hand in hand value-wise.
答案1
得分: 3
根据您的要求，以下是翻译好的部分：
"As your bash is recent enough you could simply make VAR2 a nameref of VAR1:"
（由于您的Bash版本足够新，您可以简单地将 VAR2 设为 VAR1 的 nameref：）
"Note that the association is symmetrical:"
（请注意，关联是对称的：）
"(but they are not equivalent, VAR2 is a nameref, VAR1 is not; for instance, to unset VAR1 you just unset VAR1, while to really unset VAR2 you need the -n option of unset, else, with unset VAR2, you unset VAR1)."
（但它们并不等同，VAR2 是一个 nameref，VAR1 不是；例如，要取消设置 VAR1，您只需执行 unset VAR1，而要真正取消设置 VAR2，您需要使用 unset 命令的 -n 选项，否则，使用 unset VAR2 会取消设置 VAR1。）
英文:
As your bash is recent enough you could simply make VAR2 a nameref of VAR1:
$ declare -n VAR2=VAR1
$ VAR1=foo
$ echo $VAR2
foo
Note that the association is symmetrical:
$ VAR2=bar
$ echo $VAR1
bar
(but they are not equivalent, VAR2 is a nameref, VAR1 is not; for instance, to unset VAR1 you just unset VAR1, while to really unset VAR2 you need the -n option of unset, else, with unset VAR2, you unset VAR1).
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