在Bash中取消一个动态变量列表

Question

如何使用Bash实现以下目标：

np.array ([ True, [[5....]] ])

我基本上想要取消设置最初使用eval设置的变量。

Answer 1

您可以分叉子shell，在子shell中执行eval，一旦完成，退出子shell：

# do this in a subshell
(
x="search='something' replace='something' subject=/path"
eval "$x"
echo "search=$search"
)

# now out of subshell
echo "search=$search"

Answer 2

序言：谨慎使用eval作为eval is evil ...
无论...

bash可以很快完成此任务：

unset ${x//=*([^ ])}

正如glenn jackman所指出的那样，只有在变量内容中没有空格时才能正常工作。

在这种情况下，我们可以（很快）准备一些中间变量（ x without spaces ）：

xwos=${x//\"*([^\"])\"}        # This will drop `search="don't know"`
xwos=${xwos//\'*([^\'])\'}     # This will drop `search='blah blah'`
unset ${xwos//=*([^ ])}

很好，将其添加到您的脚本中将完成这项工作：

xwos=${x//\"*([^\"])\"}; xwos=${xwos//\'*([^\'])\'}; unset ${xwos//=*([^ ])}

说明/展示

当然，您必须使用 extglob bash的选项，如果尚未设置：

shopt -s extglob

让我们试试：

x="search='something something' replace='something' subject=/path/path"

eval "$x"

echo $search 
something something

declare -p search replace subject
declare -- search="something something"
declare -- replace="something"
declare -- subject="/path/path"

shopt -s extglob
xwos=${x//\"*([^\"])\"}
printf 'X w/o double quoted spaces 1st:\n    "%s"\n' "$xwos"
X w/o double quoted spaces 1st:
    "search='something something' replace='something' subject=/path/path"

xwos=${xwos//\'*([^\'])\'}
printf 'X w/o single quoted spaces 2nd:\n    "%s"\n' "$xwos"
X w/o single quoted spaces 2nd:
    "search= replace= subject=/path/path"

printf 'String containing variables w/o values:\n    "%s"\n' "${xwos//=*([^ ])}"
String containing variables w/o values:
    "search replace subject"

unset ${xwos//=*([^ ])}

declare -p search replace subject
bash: declare: search: not found
bash: declare: replace: not found
bash: declare: subject: not found

Nota：如果您不再需要x，则可以重新定义x，而不是填充新变量：

shopt -s extglob;x=${x//\"*([^\"])\"};x=${x//\'*([^\'])\'};unset ${x//=*([^ ])}

演示

x="search='something something' replace='something' subject=/path/path"

eval "$x"

echo $search 
something something

shopt -s extglob;x=${x//\"*([^\"])\"};x=${x//\'*([^\'])\'};unset ${x//=*([^ ])}
echo $search