Parsing Json data columnwise in shell

Question

When I run a command I get a response like this

{

    "status": "available",
    "managed": true,
    "name":vdisk7,
    "support":{
    "status": "supported"
    },
    "storage_pool": "pfm9253_pfm9254_new",
    "id": "ff10abad"-2bf-4ef3-9038-9ae7f18ea77c",
    "size":100
},

and hundreds of this type of lists or dictionaries I want a command that does such sort of a thing

if name = "something", 
    get the id

Any links that would help me in learning such sort of commands would be highly appreciated

I have tried

awk '{if ($2 == "something") print $0;}'

But I think the response is in Json so the colum wise awk formatting is not working.

Also it's just a single command that I need to run so I would prefer not to use any external library.

Have you looked at jq ? It has a convenient syntax for filtering. — SheetJS
– SheetJS, Commented Oct 22, 2013 at 7:54

chepner · Accepted Answer · 2013-10-22 14:42:19Z

14

JSON parser is better for this task

awk and sed are utilities to parse line-oriented text, but not json. What if your json formatting will change ? (some lines will go on one line ?).

You should use any standard json parser out there. Or use some powerful scripting language, such as PHP, Python, Ruby, etc.

I can provide you with example on how to do it with python.

What if I can't use powerful scripting language ?

If you totally unable to use python, then there is utility jq out there: link

If you have some recent distro, jq maybe already in repositories (example: Ubuntu 13.10 has it in repos).

I can use python!

I would do that using simple python inline script.

For example we have some some_command that returns json as a result.

We have to get value of data["name"].

Here we go:

some_command | python -c "import json, sys; print json.load(sys.stdin)['name']"

It will output vdisk7 in your case

For this to work you need to be sure, json is fully valid.

If you have a list of json objects:

[
  {
    ...
    "name": "vdisk17"
    ...
  },
  {
    ...
    "name": "vdisk18"
    ...
  },
  {
    ...
    "name": "vdisk19"
    ...
  },
...
]

You could use some list comprehensions:

some_command | python -c "import json, sys; [sys.stdout.write(x['name'] + '\n') for x in json.load(sys.stdin)]"

It will output:

vdisk17
vdisk18
vdisk19

edited Oct 22, 2013 at 14:42

chepner

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answered Oct 22, 2013 at 7:44

Waterlink

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5 Comments

The_Lost_Avatar Over a year ago

That works. But I am not allowed to use Python, simple bash commands like awk, grep , sed, head , tail , you get the idea.

Waterlink Over a year ago

What limits you from using python ? Python is in LSB (linux standard base). So it should be available on every linux distro.

The_Lost_Avatar Over a year ago

@Waterlink Would that work in AIX too ??I can't test on AIX right now but I might need to do that in a few days.

Waterlink Over a year ago

@MAD_ABOUT_JAVA I got your problem here. Then you totally unable to use python ) You can try to build jq from source.

The_Lost_Avatar Over a year ago

Yes, that's better. Thanx for the help Waterlink.

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