使用jq修改JSON [英] Modifying JSON by using jq

问题描述

我想使用Linux命令行修改JSON文件.

I want to modify a JSON file by using the Linux command line.

我尝试了以下步骤:

[root@localhost]# INPUT="dsa"
[root@localhost]# echo $INPUT
dsa
[root@localhost]# CONF_FILE=test.json
[root@localhost]# echo $CONF_FILE
test.json
[root@localhost]# cat $CONF_FILE
{
  "global" : {
    "name" : "asd",
    "id" : 1
  }
}
[root@localhost]# jq -r '.global.name |= '""$INPUT"" $CONF_FILE > tmp.$$.json && mv tmp.$$.json $CONF_FILE
jq: error: dsa/0 is not defined at <top-level>, line 1:
.global.name |= dsa
jq: 1 compile error

所需的输出:

[root@localhost]# cat $CONF_FILE
    {   "global" : {
    "name" : "dsa",
    "id" : 1   } }

推荐答案

您唯一的问题是传递给jq的脚本引用不正确.

Your only problem was that the script passed to jq was quoted incorrectly.

在您的特定情况下，将单个双引号字符串与嵌入的\转义的"实例一起使用可能是最简单的:

In your particular case, using a single double-quoted string with embedded \-escaped " instances is probably simplest:

jq -r ".global.name = \"$INPUT\"" "$CONF_FILE" > tmp.$$.json && mv tmp.$$.json "$CONF_FILE"

但是，通常， chepner的有用答案显示了将shell变量引用直接嵌入到其中的更健壮的选择脚本:使用 --arg选项传递值作为jq 变量允许单引号 ，这是更好的选择，因为它避免了shell预先扩展了哪些元素的混淆，并且避免了转义应传递给jq的$实例的需要.

Generally, however, chepner's helpful answer shows a more robust alternative to embedding the shell variable reference directly in the script: Using the --arg option to pass a value as a jq variable allows single-quoting the script, which is preferable, because it avoids confusion over what elements are expanded by the shell up front and obviates the need for escaping $ instances that should be passed through to jq.

也:

• 只需=就足以分配值；虽然|=(所谓的更新运算符)也可以工作，但在这种情况下它的作用与=相同，因为RHS是 literal ，而不是引用LHS的表达式-请参阅手册.
• 您应该常规地将shell变量引用双引号，并且应该避免使用全大写的变量名，以便

• Just = is sufficient to assign the value; while |=, the so-called update operator, works too, it behaves the same as = in this instance, because the RHS is a literal, not an expression referencing the LHS - see the manual.
• You should routinely double-quote your shell-variable references and you should avoid use of all-uppercase variable names in order to avoid conflicts with environment variables and special shell variables.

关于为什么您的报价无效:

'.global.name |= '""$INPUT""由以下标记组成:

• 字符串文字.global.name |=(由于单引号)
• 字符串文字""-即空字符串-在jq看到脚本之前，shell将引号除去
• 对$INPUT变量的不带引号的引用(使它的值易于分词和通配).
• 文字""的另一个实例.

• String literal .global.name |= (due to single-quoting)
• String literal "" - i.e., the empty string - the quotes will be removed by the shell before jq sees the script
• An unquoted reference to variable $INPUT (which makes its value subject to word-splitting and globbing).
• Another instance of literal "".

使用您的样本值，jq最终看到以下字符串作为其脚本:

With your sample value, jq ended up seeing the following string as its script:

.global.name |= dsa

如您所见，双引号丢失了，导致jq将dsa解释为函数名而不是字符串文字，并且由于没有将参数传递给(函数dsa存在，jq的错误消息将其引用为dsa/0-没有(0)参数的函数.

As you can see, the double quotes are missing, causing jq to interpret dsa as a function name rather than a string literal, and since no argument was passed to (non-existent) function dsa, jq's error message referenced it as dsa/0 - a function with no (0) arguments.

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