使用 jq 检查字符串是否是有效的 JSON
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Check if string is a valid JSON with jq
提问by Milkncookiez
I need to catch an error when lifting a service. The response can be null, a string error message like
提升服务时我需要捕获错误。响应可以是null一个字符串错误消息，如
error services-migration/foobar: Not found: services-migration/foobar
error services-migration/foobar: Not found: services-migration/foobar
or a valid JSON when everything is fine. I was wondering if there is a way with jqto simply check if the provided string is a valid JSON. I could ofc check the string for some keywords like errorf.e., but I'm looking for a more robust option, where eg. I get a true/falseor 1/0from jq.
I was looking through the docs of jqand also some questions here on SO but everything was about finding and picking out key-values from a JSON, but nothing about simply validating a string.
或者当一切正常时有效的 JSON。我想知道是否有一种方法jq可以简单地检查提供的字符串是否是有效的 JSON。我可以检查某些关键字的字符串，例如errorfe，但我正在寻找更强大的选项，例如。我从 jq得到 atrue/false或1/0。我正在查看jq关于 SO的文档和一些问题，但一切都是关于从 JSON 中查找和挑选键值，而不是简单地验证字符串。
UPDATE:
更新：
I've got this:
我有这个：
result=$(some command)
from which the result is the string error services-migration/foobar: Not found: services-migration/foobar
结果是字符串 error services-migration/foobar: Not found: services-migration/foobar
And then the if statement:
然后是 if 语句：
if jq -e . >/dev/null 2>&1 <<<"$result"; then
echo "it catches it"
else
echo "it doesn't catch it"
fi
And it always ends up in the elseclause.
它总是以else子句结尾。
采纳答案by Tom Fenech
From the manual:
从手册：
-e / --exit-status:
Sets the exit status of jq to 0 if the last output values was neither false nor null, 1 if the last output value was either false or null, or 4 if no valid result was ever produced. Normally jq exits with 2 if there was any usage problem or system error, 3 if there was a jq program compile error, or 0 if the jq program ran.
-e / --exit-status:
如果最后一个输出值既不是假也不是空，则将 jq 的退出状态设置为 0，如果最后一个输出值是假或空，则设置为 1，如果没有产生有效结果，则设置为 4。通常，如果出现任何使用问题或系统错误，jq 以 2 退出，如果存在 jq 程序编译错误，则以 3 退出，如果 jq 程序运行则以 0 退出。
So you can use:
所以你可以使用：
if jq -e . >/dev/null 2>&1 <<<"$json_string"; then
echo "Parsed JSON successfully and got something other than false/null"
else
echo "Failed to parse JSON, or got false/null"
fi
In fact, if you don't care about distinguishing between the different types of error, then you can just lose the -eswitch. In this case, anything considered to be valid JSON (including false/null) will be parsed successfully by the filter .and the program will terminate successfully, so the ifbranch will be followed.
事实上，如果您不在乎区分不同类型的错误，那么您可能会失去-e开关。在这种情况下，任何被认为是有效 JSON（包括 false/null）的东西都将被过滤器成功解析.，程序将成功终止，因此if将遵循分支。
回答by Reddy SK
This is working for me
这对我有用
echo $json_string | jq -e . >/dev/null 2>&1 | echo ${PIPESTATUS[1]}
that returns return code:
返回返回码：
- 0 - Success
- 1 - Failed
- 4 - Invalid
- 0 - 成功
- 1 - 失败
- 4 - 无效
Then you can evaluate the return code by further code.
然后您可以通过进一步的代码评估返回码。
