Question 284657 in Docker Question posted in
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Docker – Access array list item by name using jq

Consider the following json data, sourced from from Docker image nginx:1.25-bookworm:

# docker pull nginx:1.25-bookworm
# docker image inspect 81be38025439 | jq '.[].Config.Env'
[
  "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
  "NGINX_VERSION=1.25.3",
  "NJS_VERSION=0.8.2",
  "PKG_RELEASE=1~bookworm"
]
#

I would like to be able to access ‘1.25.3’ from this list to tag the image in a build step of a CI-CD pipeline.

I am close to my goal with the following:

# docker image inspect 0743972990c7 | jq -r '.[].Config.Env[1]'
NGINX_VERSION=1.23.4

But would like to know how to access the item ‘NGINX_VERSION’ by name instead of relying on the assumption that it will be the second environment variable.

Tags:

2

Answers


  1. 0

    So filter NGINX_VERSION from the array and remove it.

    .[].Config.Env |
select(startswith("NGINX_VERSION=")) |
sub("^NGINX_VERSION="; "")
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  2. 0

    For the task given, I’d also go with startswith as described in KamilCuk’s answer. But if you need to access multiple values, you might want to consider creating a lookup object using INDEX:

    INDEX(.[:index("=")]) as $ix   # stores {"PATH": … , "NGINX_VERSION": … , …}

    and then access the values by field name (truncate by the index position of the first = character):

    | $ix["NGINX_VERSION"]         # yields "NGINX_VERSION=1.25.3"
| .[index("=")+1:]             # yields "1.25.3

    Demo

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