问题

I have translated the provided content for you:

我有类似的文件/数据：

```bash
$ echo "[{\"my_var1\":\"valueA\", \"my_var2\": \"valueB\"}]"
{"my_var1":"valueA", "my_var2": "valueB"}]

在我的代码中，我需要获取“my_var2”的值，很容易：

$ echo "[{\"my_var1\":\"valueA\", \"my_var2\": \"valueB\"}]" | \
jq -r ''.[] .my_var2''

# 正确的结果：
valueB

... 但是... 我需要使用bash变量来指定我想要获取的变量：

我不能指定“my_var2”，我必须只使用“var2”：

$ PART="var2"
$ echo "[{\"my_var1\":\"valueA\", \"my_var2\": \"valueB\"}]" | \
jq -r --arg JSONPART ${PART} ''.[] .my_[$JSONPART]''

期望的结果：

valueB

Please note that I've translated the content as requested, including the code portions.

<details>
<summary>英文:</summary>

I have similar file/data:

$ echo "[{"my_var1":"valueA", "my_var2": "valueB"}]"
{"my_var1":"valueA", "my_var2": "valueB"}]

in my code I need to get value of "my_var2", easy:

$ echo "[{"my_var1":"valueA", "my_var2": "valueB"}]" |
jq -r '.[] .my_var2'

correct result:

valueB

... but ... I need to use bash variable to specify which variable I would like to get:

I can't specify "my_var2", I have to use only "var2"

$ PART="var2"
$ echo "[{"my_var1":"valueA", "my_var2": "valueB"}]" |
jq -r --arg JSONPART ${PART} '.[] .my_[$JSONPART]'

expected result:

valueB

</details>


# 答案1
**得分**: 2

The jq filter `.xyz` can be rewritten as `.[&quot;xyz&quot;]`. Thus:

```shell
$ PART=&#39;var2&#39;
$ echo &#39;[{&quot;my_var1&quot;:&quot;valueA&quot;, &quot;my_var2&quot;: &quot;valueB&quot;}]&#39; | \
jq -r --arg JSONPART &quot;$PART&quot; &#39;.[][&quot;my_&quot; + $JSONPART]&#39;
valueB

(Don't forget to properly quote your shell parameters when expanding!)

$ PART='var2'
$ echo '[{"my_var1":"valueA", "my_var2": "valueB"}]' | \
jq -r --arg JSONPART "$PART" '.[]["my_" + $JSONPART]'
valueB

答案2

得分: -1

This should work:

$ PART="var2"
$ echo "[{\"my_var1\":\"valueA\", \"my_var2\": \"valueB\"}]" | \
jq -r ".[] .my_$PART"

$ PART="var2"
$ echo "[{\"my_var1\":\"valueA\", \"my_var2\": \"valueB\"}]" | \
jq -r ".[] .my_$PART"