bash output to json format

Question

I'm new to Linux and Bash scripting. I am trying to output several bash scripts in Ubuntu Linux into JSON format, however, I cannot seem to get it to work properly.

My goal is to get this:

date -u +%Y-%m-%d:%H:%M:%S  //date and time

lsb_release -a  //os distro version

ifconfig -a  //ip info

Into this format in JSON:

  "datetime":datetime_string,

  "osversion":string,

  "ip_info:  [{"interface":string,"ip_addr":string,"mask":string,"gateway":string},
             {"interface":string,"ip_addr":string,"mask":string,"gateway":string}],

Also, don't use ifconfig; it's an ancient tool nobody has maintained in over a decade. If you want to list IPs on Linux in a way that works with new and modern parts of the network stack, use ip -o addr list. — Charles Duffy, Commented Mar 24, 2016 at 20:39
...btw, gateway isn't present in the output of ifconfig -a. Since the routing table isn't interface-specific, one wouldn't really expect them to be stored/managed together... — Charles Duffy, Commented Mar 24, 2016 at 20:55
Charles, how can I output that format without having to install additional packages on the distro? I am trying to avoid having to install additional packages as much as possible. — PowerUp, Commented Mar 28, 2016 at 13:14
Using a language with a built-in JSON module -- such as Python -- is your best bet, then. — Charles Duffy, Commented Mar 28, 2016 at 14:34

Charles Duffy · Accepted Answer · 2016-03-28 17:34:27Z

Bash itself has no JSON support. Thus, to guarantee conformance, you need to use an external utility with JSON parsing and generation support built in. jq is one of these, and the below uses its built-in regex support:

jq --raw-input \
   --arg date "$(date)" \
   --arg osver "$(lsb_release -a)" \
   '{"date": $date,
     "osver": $osver,
     "ip_info": [inputs |
                 capture("^[0-9]+: (?<ifname>[^[:space:]]+)[[:space:]]+inet (?<addr>[^[:space:]/]+)(/(?<masklen>[[:digit:]]+))?")
                ]
    }' \
   < <(ip -o addr list | grep 'inet ')

See this code in action on JQPlay.

If you can't install tools not built into your Linux distro, consider Python:

#!/bin/bash
#      ^^^^ - important, not /bin/sh; this uses some bash-only syntax

py_code=$(cat <<'EOF'
import json, re, sys

content={'ip_info': []}
for k, v in [ arg.split('=', 1) for arg in sys.argv[2:] if '=' in arg ]:
  content[k]=v

ip_re = re.compile(r'^[0-9]+:\s+(?P<ifname>\S+)\s+inet (?P<addr>[^/\s]+)(?:/(?P<masklen>\d+))?')
for line in open(sys.argv[1]).readlines():
  m = ip_re.match(line)
  if not m: raise "NOOOO"
  content['ip_info'].append({
    'ifname': m.groups('ifname'),
    'addr': m.groups('addr'),
    'masklen': m.groups('masklen'),
  })

print json.dumps(content)
EOF
)

python -c "$py_code" \
  <(ip -o addr list | grep 'inet ') \
  "date=$(date)" "osver=$(lsb_release -a)"

Charles, how do I write this in Python 2.6.5 without jq?
– PowerUp
Commented Mar 28, 2016 at 15:17 — PowerUp, Commented Mar 28, 2016 at 15:17
@Fadiddy, see the extended/amended answer.
– Charles Duffy
Commented Mar 28, 2016 at 17:33 — Charles Duffy, Commented Mar 28, 2016 at 17:33

tschoffelen · Accepted Answer · 2016-03-24 20:46:14Z

0

Something like that should be quite easy to do with jo:

jo datetime=$(date -u +%Y-%m-%d:%H:%M:%S) osversion=$(lsb_release -a) ip_info=$(jo -a $(ip -o addr list))

answered Mar 24, 2016 at 20:46

tschoffelen

5207 silver badges23 bronze badges

How does jo parse ip -o addr list into fields here? I don't see how it could get the desired output format.
– Charles Duffy
Commented Mar 24, 2016 at 20:49
1

Also, you need more quotes to prevent the shell from string-splitting your key/value pairs before they're passed to jo.
– Charles Duffy
Commented Mar 24, 2016 at 20:50

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