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}],

• Charles Duffy: jq -- stedolan.github.io/jq -- is your friend.
• Charles Duffy: 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: ...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...
• PowerUp: 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.
• Charles Duffy: Using a language with a built-in JSON module -- such as Python -- is your best bet, then.

Answer 1

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)"

• PowerUp: Charles, how do I write this in Python 2.6.5 without jq?
• Charles Duffy: @Fadiddy, see the extended/amended answer.

Answer 2

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))

• Charles Duffy: 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: Also, you need more quotes to prevent the shell from string-splitting your key/value pairs before they're passed to jo.