How to fetch the content from same tag from GitHub Api using bash

I want to get the data of tag_name from this link

https://api.github.com/repos/checkstyle/checkstyle/releases

but as we have a lot of releases. How can I get a particular tag_name

I do

LATEST_RELEASE_TAG=$(curl -s https://api.github.com/repos/checkstyle/checkstyle/releases/latest \
                       | jq ".tag_name")

to get the latest tag_name but how to fetch the second tag_name?

eg:

[   {
    "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/73283356",
    "assets_url": "https://api.github.com/repos/checkstyle/checkstyle/releases/73283356/assets",
    "upload_url": "https://uploads.github.com/repos/checkstyle/checkstyle/releases/73283356/assets{?name,label}",
    "html_url": "https://github.com/checkstyle/checkstyle/releases/tag/checkstyle-10.3.2",
    "id": 73283356,
    "author": {
      "login": "romani",
      "id": 812984,
      "node_id": "MDQ6VXNlcjgxMjk4NA==",
      "avatar_url": "https://avatars.githubusercontent.com/u/812984?v=4",
      "gravatar_id": "",
      "url": "https://api.github.com/users/romani",
      "html_url": "https://github.com/romani",
      "followers_url": "https://api.github.com/users/romani/followers",
      "following_url": "https://api.github.com/users/romani/following{/other_user}",
      "gists_url": "https://api.github.com/users/romani/gists{/gist_id}",
      "starred_url": "https://api.github.com/users/romani/starred{/owner}{/repo}",
      "subscriptions_url": "https://api.github.com/users/romani/subscriptions",
      "organizations_url": "https://api.github.com/users/romani/orgs",
      "repos_url": "https://api.github.com/users/romani/repos",
      "events_url": "https://api.github.com/users/romani/events{/privacy}",
      "received_events_url": "https://api.github.com/users/romani/received_events",
      "type": "User",
      "site_admin": false
    },
    "node_id": "RE_kwDOAL65M84EXjcc",
    "tag_name": "checkstyle-10.3.2",
    "target_commitish": "master",
    "name": "",
    "draft": false,
    "prerelease": false,
    "created_at": "2022-07-31T13:38:47Z",
    "published_at": "2022-07-31T13:54:14Z",
    "assets": [
      {
        "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/assets/73245332",
        "id": 73245332,
        "node_id": "RA_kwDOAL65M84EXaKU",
        "name": "checkstyle-10.3.2-all.jar",
        "label": "",
        "uploader": {
          "login": "romani",
          "id": 812984,
          "node_id": "MDQ6VXNlcjgxMjk4NA==",
          "avatar_url": "https://avatars.githubusercontent.com/u/812984?v=4",
          "gravatar_id": "",
          "url": "https://api.github.com/users/romani",
          "html_url": "https://github.com/romani",
          "followers_url": "https://api.github.com/users/romani/followers",
          "following_url": "https://api.github.com/users/romani/following{/other_user}",
          "gists_url": "https://api.github.com/users/romani/gists{/gist_id}",
          "starred_url": "https://api.github.com/users/romani/starred{/owner}{/repo}",
          "subscriptions_url": "https://api.github.com/users/romani/subscriptions",
          "organizations_url": "https://api.github.com/users/romani/orgs",
          "repos_url": "https://api.github.com/users/romani/repos",
          "events_url": "https://api.github.com/users/romani/events{/privacy}",
          "received_events_url": "https://api.github.com/users/romani/received_events",
          "type": "User",
          "site_admin": false
        },
        "content_type": "application/zip",
        "state": "uploaded",
        "size": 16208747,
        "download_count": 505,
        "created_at": "2022-07-31T13:54:16Z",
        "updated_at": "2022-07-31T13:55:12Z",
        "browser_download_url": "https://github.com/checkstyle/checkstyle/releases/download/checkstyle-10.3.2/checkstyle-10.3.2-all.jar"
      }
    ],
    "tarball_url": "https://api.github.com/repos/checkstyle/checkstyle/tarball/checkstyle-10.3.2",
    "zipball_url": "https://api.github.com/repos/checkstyle/checkstyle/zipball/checkstyle-10.3.2",
    "body": "https://checkstyle.org/releasenotes.html#Release_10.3.2\r\n\r\nBug fixes:\r\n\r\n  #11736 - MissingJavadocType: Support qualified annotation names\r\n  #11655 - Update google_checks.xml to have the SuppressionCommentFilter and SuppressWarningsHolder modules in the config by default (and by extension, SuppressWarningsFilter)\r\n\r\n<details>\r\n<summary>Other Changes:</summary>\r\n<br>\r\n  Update releasenotes to use GitHub Pages execution\r\n<br />\r\n  Allow SuppressWarningHolder to suppress the violation with NameCheck\r\n<br />\r\n  Pitest: Kill all surviving mutations\r\n<br />\r\n  Pitest: Activate \"ALL\" mutator group\r\n<br />\r\n  Use Shellcheck to resolve violations code in Shell Script\r\n<br />\r\n  pitest: increase mutation coverage for pitest-imports profile to 100% \r\n<br />\r\n  Update GitHub Action for bump-license-year.sh\r\n<br />\r\n  Solve fb-contrib errors\r\n<br />\r\n  Remove pitest mutation checking HTML model\r\n<br />\r\n  automate execution by Github action bump-license-year.sh on first day of month\r\n<br />\r\n  update code base to have javadoc tag to explain noinspection tag content\r\n<br />\r\n  doc: put example of enableExternalDtdLoad to xdoc\r\n<br />\r\n  update doc for SuppressWarningsHolder\r\n<br />\r\n  releasenotes script generated empty commit\r\n<br />\r\n  Include CDG Accelerator Plugin to boost pitest performance\r\n<br />\r\n  Enforce file size on Java inputs\r\n<br />\r\n  Expand XPath IT Regression Testing\r\n<br />\r\n There are semantic problems in the Chinese error message of keyword `design.forExtension` .\r\n<br />\r\n  prepare-settings.sh fails to create settings.xml\r\n<br />\r\n  Use groovy version provided by `apt` in pitest.yml\r\n<br />\r\n  tweet-releasenotes.sh does not check env variables\r\n<br />\r\n  download of m2 cache from sourceforge.io is slow \r\n<br />\r\n  infra: turns off create dependency reduced pom for shade plugin\r\n<br />\r\n  Update Tests to use new 'verifyXxxxxx' method or 'execute' that use inlined config in Input files\r\n<br />\r\n  Specify violation messages in input files.\r\n<br />\r\n  pitest: increase mutation coverage for javadoc profile to 100%\r\n<br />\r\n</details>",
    "reactions": {
      "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/73283356/reactions",
      "total_count": 10,
      "+1": 0,
      "-1": 0,
      "laugh": 0,
      "hooray": 6,
      "confused": 0,
      "heart": 2,
      "rocket": 2,
      "eyes": 0
    }   },   {
    "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/70647006",
    "assets_url": "https://api.github.com/repos/checkstyle/checkstyle/releases/70647006/assets",
    "upload_url": "https://uploads.github.com/repos/checkstyle/checkstyle/releases/70647006/assets{?name,label}",
    "html_url": "https://github.com/checkstyle/checkstyle/releases/tag/checkstyle-10.3.1",
    "id": 70647006,
    "author": {
      "login": "romani",
      "id": 812984,
      "node_id": "MDQ6VXNlcjgxMjk4NA==",
      "avatar_url": "https://avatars.githubusercontent.com/u/812984?v=4",
      "gravatar_id": "",
      "url": "https://api.github.com/users/romani",
      "html_url": "https://github.com/romani",
      "followers_url": "https://api.github.com/users/romani/followers",
      "following_url": "https://api.github.com/users/romani/following{/other_user}",
      "gists_url": "https://api.github.com/users/romani/gists{/gist_id}",
      "starred_url": "https://api.github.com/users/romani/starred{/owner}{/repo}",
      "subscriptions_url": "https://api.github.com/users/romani/subscriptions",
      "organizations_url": "https://api.github.com/users/romani/orgs",
      "repos_url": "https://api.github.com/users/romani/repos",
      "events_url": "https://api.github.com/users/romani/events{/privacy}",
      "received_events_url": "https://api.github.com/users/romani/received_events",
      "type": "User",
      "site_admin": false
    },
    "node_id": "RE_kwDOAL65M84ENfze",
    "tag_name": "checkstyle-10.3.1",
    "target_commitish": "master",
    "name": "",
    "draft": false,
    "prerelease": false,
    "created_at": "2022-06-27T13:50:30Z",
    "published_at": "2022-06-27T14:07:12Z",
    "assets": [
      {
        "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/assets/69790751",
        "id": 69790751,
        "node_id": "RA_kwDOAL65M84EKOwf",
        "name": "checkstyle-10.3.1-all.jar",
        "label": "",
        "uploader": {
          "login": "romani",
          "id": 812984,
          "node_id": "MDQ6VXNlcjgxMjk4NA==",
          "avatar_url": "https://avatars.githubusercontent.com/u/812984?v=4",
          "gravatar_id": "",
          "url": "https://api.github.com/users/romani",
          "html_url": "https://github.com/romani",
          "followers_url": "https://api.github.com/users/romani/followers",
          "following_url": "https://api.github.com/users/romani/following{/other_user}",
          "gists_url": "https://api.github.com/users/romani/gists{/gist_id}",
          "starred_url": "https://api.github.com/users/romani/starred{/owner}{/repo}",
          "subscriptions_url": "https://api.github.com/users/romani/subscriptions",
          "organizations_url": "https://api.github.com/users/romani/orgs",
          "repos_url": "https://api.github.com/users/romani/repos",
          "events_url": "https://api.github.com/users/romani/events{/privacy}",
          "received_events_url": "https://api.github.com/users/romani/received_events",
          "type": "User",
          "site_admin": false
        },
        "content_type": "application/zip",
        "state": "uploaded",
        "size": 15396315,
        "download_count": 3577,
        "created_at": "2022-06-27T14:07:13Z",
        "updated_at": "2022-06-27T14:08:06Z",
        "browser_download_url": "https://github.com/checkstyle/checkstyle/releases/download/checkstyle-10.3.1/checkstyle-10.3.1-all.jar"
      }
    ],
    "tarball_url": "https://api.github.com/repos/checkstyle/checkstyle/tarball/checkstyle-10.3.1",
    "zipball_url": "https://api.github.com/repos/checkstyle/checkstyle/zipball/checkstyle-10.3.1",
    "body": "https://checkstyle.org/releasenotes.html#Release_10.3.1",
    "reactions": {
      "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/70647006/reactions",
      "total_count": 8,
      "+1": 0,
      "-1": 0,
      "laugh": 0,
      "hooray": 7,
      "confused": 0,
      "heart": 1,
      "rocket": 0,
      "eyes": 0
    }   },

This has 2 tag_name and I want to fetch the data of the second tag_name. Now It's like I always want the 2nd number tag_name only.

-> I want to use this tag_name as the previous release so I want the latest tag_name as the latest tag and the 2nd tag "tag_name" as the previous tag. I want to use these in a shell script.

Solution

Fetching the Two Most Recent Release

You can have the Github releases API respond with the two most recent releases, and then use jq to access all .tag_name fields in the array objects and then read them into separate bash variables, like so:

#!/bin/bash

# You only care about the latest release and previous, so you can
# pass the per_page query parameter
github_rsp="$(curl -s https://api.github.com/repos/checkstyle/checkstyle/releases?per_page=2)"

# jq lets you access multiple objects in a list
# using different syntaxes. Here, ".[].tag_name" will just
# access every tag_name field in each object of the response array
# and then we put those into an array that we then join with ";'

# We then read jq's output into two separate shell variables
# using ";' as our separator

IFS=";" read latest previous < <(jq -r '[.[].tag_name] | join(";")' <<< $github_rsp)

echo "  Latest version: $latest"
echo "Previous version: $previous"

With this as output

❯ ./parse.sh
  Latest version: checkstyle-10.3.2
Previous version: checkstyle-10.3.1

Also see the following for even more info about how my script works, if you need explanation beyond my notes:

Fetching a Single Release

Since you asked about getting any arbitrary release, if you have a tag name, you can use the Github Release-by-Tag API, where you put a specific tag into the releases API URL.

#!/bin/bash

function get_release() {
    local repo="$1"
    local tag="$2"
    local release_url="https://api.github.com/repos/${repo}/releases/tags/${tag}"
    rsp=$(curl -s -H 'Accept: application/vnd.github+json' "$release_url")
    echo "$rsp"
}

get_release "checkstyle/checkstyle" "checkstyle-10.1" | jq

And running this script I get...

❯ ./single-release.sh
{
  "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/62869604",
  "assets_url": "https://api.github.com/repos/checkstyle/checkstyle/releases/62869604/assets",
  "upload_url": "https://uploads.github.com/repos/checkstyle/checkstyle/releases/62869604/assets{?name,label}",
  "html_url": "https://github.com/checkstyle/checkstyle/releases/tag/checkstyle-10.1",
  "id": 62869604,
  "author": {
    "login": "romani",
    "id": 812984,
    "node_id": "MDQ6VXNlcjgxMjk4NA==",
    "avatar_url": "https://avatars.githubusercontent.com/u/812984?v=4",
    "gravatar_id": "",
    "url": "https://api.github.com/users/romani",
    "html_url": "https://github.com/romani",
    "followers_url": "https://api.github.com/users/romani/followers",
    "following_url": "https://api.github.com/users/romani/following{/other_user}",
    "gists_url": "https://api.github.com/users/romani/gists{/gist_id}",
    "starred_url": "https://api.github.com/users/romani/starred{/owner}{/repo}",
    "subscriptions_url": "https://api.github.com/users/romani/subscriptions",
    "organizations_url": "https://api.github.com/users/romani/orgs",
    "repos_url": "https://api.github.com/users/romani/repos",
    "events_url": "https://api.github.com/users/romani/events{/privacy}",
    "received_events_url": "https://api.github.com/users/romani/received_events",
    "type": "User",
    "site_admin": false
  },
  "node_id": "RE_kwDOAL65M84Dv1Bk",
  "tag_name": "checkstyle-10.1",
  "target_commitish": "master",
  "name": "",
  "draft": false,
  "prerelease": false,
  "created_at": "2022-03-27T14:51:31Z",
  "published_at": "2022-03-27T15:06:48Z",
  "assets": [
    {
      "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/assets/60754101",
      "id": 60754101,
      "node_id": "RA_kwDOAL65M84Dnwi1",
      "name": "checkstyle-10.1-all.jar",
      "label": "",
      "uploader": {
        "login": "romani",
        "id": 812984,
        "node_id": "MDQ6VXNlcjgxMjk4NA==",
        "avatar_url": "https://avatars.githubusercontent.com/u/812984?v=4",
        "gravatar_id": "",
        "url": "https://api.github.com/users/romani",
        "html_url": "https://github.com/romani",
        "followers_url": "https://api.github.com/users/romani/followers",
        "following_url": "https://api.github.com/users/romani/following{/other_user}",
        "gists_url": "https://api.github.com/users/romani/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/romani/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/romani/subscriptions",
        "organizations_url": "https://api.github.com/users/romani/orgs",
        "repos_url": "https://api.github.com/users/romani/repos",
        "events_url": "https://api.github.com/users/romani/events{/privacy}",
        "received_events_url": "https://api.github.com/users/romani/received_events",
        "type": "User",
        "site_admin": false
      },
      "content_type": "application/zip",
      "state": "uploaded",
      "size": 13403044,
      "download_count": 6227,
      "created_at": "2022-03-27T15:06:49Z",
      "updated_at": "2022-03-27T15:07:35Z",
      "browser_download_url": "https://github.com/checkstyle/checkstyle/releases/download/checkstyle-10.1/checkstyle-10.1-all.jar"
    }
  ],
  "tarball_url": "https://api.github.com/repos/checkstyle/checkstyle/tarball/checkstyle-10.1",
  "zipball_url": "https://api.github.com/repos/checkstyle/checkstyle/zipball/checkstyle-10.1",
  "body": "https://checkstyle.org/releasenotes.html#Release_10.1",
  "reactions": {
    "url": "https://api.github.com/repos/checkstyle/checkstyle/releases/62869604/reactions",
    "total_count": 4,
    "+1": 1,
    "-1": 0,
    "laugh": 0,
    "hooray": 3,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
  }
}