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

Question

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.

Answer 1

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:
jq Object Value Iterator
Github REST API - List Releases
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
}
}