check value of json response in bash script

Question

{"running": 1, "finished": 3, "node_name": "L-2.local", "pending": 0, "status": "ok"}

I'm trying to parse this response to check the value of "running" with a bash script. I know there's libraries to do this, but some reason the jq library wouldn't install, and I prefer not to install it, as I only need it for this one command. Normally I'd use Python instead.

I tried using this command from another answer, on the response

| grep -Po '"running":"\K[^,]*'

but it failed due to the "."

bash: {"running": 0, "finished": 0, "node_name": "L-2: command not found

Is there a way to get it to check the value of "running" with grep, and not have the error?

You have a " in the pattern after :, but there is no quote in the string. Use echo '...string...' | grep -Po '"running":\s*\K[^,]+'. If you are sure there are digits only, use '"running":\s*\K\d+' — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 28, 2017 at 7:18
Thanks, I meant to add the version without the quote. I now discovered the -P option doesn't work with OSX, so can't get it to work yet. — Matts
– Matts, Commented Jul 28, 2017 at 10:44
You may use sed to get the value, though it won't look pretty. See my answer. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 28, 2017 at 10:59

EMottet · Accepted Answer · 2017-07-28 07:16:14Z

3

First, this error bash: {"running": 0, "finished": 0, "node_name": "L-2: command not found is because you don't use echo before your expression.

use : echo '{"running": 1, "finished": 3, "node_name": "L-2.local", "pending": 0, "status": "ok"}' | grep -Po '"running":\s*\K\d+'

answered Jul 28, 2017 at 7:16

EMottet

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Wiktor Stribiżew · Accepted Answer · 2017-07-28 10:54:53Z

1

You may use sed to remove what you do not need and only capture and keep what you need using a capturing group and a backreference:

s='{"running": 1, "finished": 3, "node_name": "L-2.local", "pending": 0, "status": "ok"}'
echo $s | sed 's/.*"running":[[:space:]]*\([0-9]*\).*/\1/'

See the online demo.

Pattern details

.* - any 0+ chars as many as possible
"running": - a literal substring
[[:space:]]* - 0+ whitespaces
\([0-9]*\) - a capturing group (note the escapes, they are necessary since the pattern is POSIX BRE compliant) matching 0 or more digits
.* - the rest of the line.

The \1 is the backreference to the Group 1 value.

answered Jul 28, 2017 at 10:54

Wiktor Stribiżew

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