how to extract a ip address from command result and store result in a variable

Question

How to extract the IP address of the output of the gcloud command mentioned bellow?

The goal is to extract the IP_ADRESS where TARGET contains targetPools and store it in a variable.

$ gcloud compute forwarding-rules list
>output:

NAME: abc
REGION: us
IP_ADDRESS: 00.000.000.000
IP_PROTOCOL: abc
TARGET: us/backendServices/abc

NAME: efg
REGION: us
IP_ADDRESS: 11.111.111.111
IP_PROTOCOL: efg
TARGET: us/targetPools/efg

desired output:

IP="11.111.111.111" 

my attempt:

IP=$(gcloud compute forwarding-rules list | grep "IP_ADDRESS")

it doesn't work bc it need to

1. get the one with TARGET contains targetPools
2. extract the IP_ADRESS
3. store in local variable to be used

But not sure how to do this, any hints?

Answer 1

With your given input, you could chain a few commands with pipes. That means there is always one line of text/string in between TARGET and IP_ADDRESS.

gcloud ... 2>&1 | grep -FB2 'TARGET: us/targetPools/efg' | head -n1 | sed 's/^.*: *//'

---

You could do without the head, something like

gcloud ... 2>&1 | grep -FB2 'TARGET: us/targetPools/efg' | sed 's/^.*: *//;q'

---

Some code explanation.

• 2>&1 Is a form of shell redirection, it is there to capturestderr and stdout.

• -FB2 is a shorthand for -F -B 2

  • See grep --help | grep -- -B
  • See grep --help | grep -- -F

• sed 's/^.*: *//'

  • ^ Is what they call an anchor, it means from the start.

  • .* Means zero or more character/string.

    • . Will match a single string/character

    • * Is what they call a quantifier, will match zero or more character string

  • : Is a literal : in this context

  • * Will match a space, (zero or more)

  • // Remove what ever is/was matched by the pattern.

  • q means quit, without it sed will print/output all the lines that was matched by grep