如何用 shell 脚本替换 json 文件的参数？

Question

Let's say 123.json with below content:

{
  "LINE" : {
    "A_serial" : "1234",
    "B_serial" : "2345",
    "C_serial" : "3456",
    "X_serial" : "76"
  }
}

If I want to use a shell script to change the parameter of X_serial by the original number +1 which is 77 in this example. I have tried the below script to take out the parameter of X_serial :

grep "X_serial" 123.json | awk {print"$3"}

which outputs 76 . But then I don't know how to make it into 77 and then put it back to the parameter of X_serial .

Answer 1

It's not a good idea to use line-oriented tools for parsing/manipulating JSON data. Use jq instead, for example:

$ jq '.LINE.X_serial |= "\(tonumber + 1)"' 123.json
{
  "LINE": {
    "A_serial": "1234",
    "B_serial": "2345",
    "C_serial": "3456",
    "X_serial": "77"
  }
}

This simply updates .LINE.X_serial by converting its value to a number, increasing the result by one, and converting it back to a string.

Answer 2

You need to install powerful JSON querying processor like jq processor. you can can easily install from here

once you install jq processor, try following command to extract the variable from JSON key value

value=($(jq -r '.X_serial' yourJsonFile.json))

you can modify the $value as you preferred operations

Answer 3

With pure Javascript: nodejs and bash :

node <<EOF
var o=$(</tmp/file);
o["LINE"]["X_serial"] = parseInt(o["LINE"]["X_serial"]) + 1;
console.log(o);
EOF

Output

{ LINE:
   { A_serial: '1234',
     B_serial: '2345',
     C_serial: '3456',
     X_serial: 78 }
}

Answer 4

sed or perl , depending on whether you just need string substitution or something more sophisticated, like arithmetic.

Since you tried grep and awk, let's start with sed:

In all lines that contain TEXT, replace foo with bar

sed -n '/TEXT/ s/foo/bar/ p'

So in your case, something like:

sed -n '/X_serial/ s/\"76\"/\"77\"/ p'

or

$ cat 123.json | sed  '/X_serial/ s/\"76\"/\"77\"/' > new.json

This performs a literal substiution: "76" -> "77"

If you would like to perform arithmetic, like "+1" or "+10" then use perl not sed:

$ cat 123.json | perl -pe 's/\d+/$&+10/e if /X_serial/'
{
  "LINE" : {
    "A_serial" : "1234",
    "B_serial" : "2345",
    "C_serial" : "3456",
    "X_serial" : "86"
  }
}

This operates on all lines containing X_serial (whether under "LINE" or under something else), as it is not a json parser.