Get comma separated values in shell script

Question

I have a file with multiple lines like the following string. I need to extract the values of id and obj.

{"Class":"ZONE","id":"DEV100.ZN301","name":"3109 E BTM","zgroup":"EAST FLOOR 3","prog":"","members":[{"obj":"DEV300.WC3"},{"obj":"DEV300.WC4"},{"obj":"DEV300.WC7"},{"obj":"DEV300.WC10"}]}

I am using the following command to obtain the output:

[user@server ~]$ cat file.txt | grep "\"Class\":\"ZONE\"" | while IFS="," read -r a b c d e f ; do echo "$b$f";done | grep ZN301

Output:

"id":"DEV100.ZN301""members":[{"obj":"DEV300.WC3"},{"obj":"DEV300.WC4"},{"obj":"DEV300.WC7"},{"obj":"DEV300.WC10"}]}

My aim is to get the following Output:

DEV100.ZN301 : DEV300.WC3 , DEV300.WC4 , DEV300.WC7 , DEV300.WC10

Please help me out. Thanks!

The sane way to do this is to use jq. Trying to parse JSON with tools that don't understand its syntax is innately error-prone. — Charles Duffy
– Charles Duffy, Commented May 31, 2018 at 0:00
Keep in mind that if the program generating your files suddenly starts, say, sorting the keys, to make the lines instead look like {"Class":"ZONE","id":"DEV100.ZN301","members":[{"obj":"DEV300.WC3"},{"obj":"DEV300.WC4"},{"obj":"DEV300.WC7"},{"obj":"DEV300.WC10"}],"name":"3109 E BTM","prog":"","zgroup":"EAST FLOOR 3"}, that would have exactly the same semantics for any compliant JSON parser, but would break your code that depends on ordering utterly. And that kind of thing can happen just with library version changes and no code updates to the tool itself at all. — Charles Duffy
– Charles Duffy, Commented May 31, 2018 at 0:02

Charles Duffy · Accepted Answer · 2018-05-31 12:34:57Z

1

jq -r 'select(.Class == "ZONE") | (.id + " : " + ([.members[] | .obj] | join(" , ")))'

...or, leaning on a Python interpreter:

parse_json() {
  python -c '
import sys, json
for line in sys.stdin:
  line = line.strip()    # ignore trailing newlines
  if not line: continue  # skip blank lines
  doc = json.loads(line)
  if doc.get("Class") != "ZONE":
    continue
  line_id = doc.get("id")
  objs = [m.get("obj") for m in doc.get("members", [])]
  sys.stdout.write("%s : %s\n" % (line_id, " , ".join(objs)))
'
}

parse_json

edited May 31, 2018 at 12:34

answered May 31, 2018 at 0:09

Charles Duffy

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1 Comment

Abhishek Over a year ago

Thanks for the Answer Charles, but I cannot install custom packages on the machines and i have 1000s of such machines. So I am trying to get a shell command that will help me out.

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