SAP Tech Bytes: Exploring SAP-samples with gh and fzf

Discover repositories that might be useful for you by exploring them from the command line with a couple of powerful tools.

The SAP-samples organisation on GitHub contains many repositories with sample code on various SAP technology topics. There’s also a new show SAP Samples Spotlight on our SAP Developers YouTube channel highlighting some of these repositories. We’re not going to be able to cover all of them on the show, so here’s a way of exploring what’s on offer, using command line tools.

the%20org-sampler%20script%20in%20action

GitHub’s command line tool gh gives us the ability to explore the API surface area. The latest release (1.8.1 at the time of writing) offers pagination, result cacheing and a built-in version of jq, the JSON processor.

You can install gh and fzf locally, or even install them in the terminal of a dev space in the SAP Business Application Studio to try things out. See how we do this in the SAP TechEd 2020 Developer Keynote repository – take a look specifically at the Add tools to your dev space section.

Before you use gh for the first time, you’ll need to authenticate – use gh auth login and follow the prompts. Then you’re all set to use the org-sampler script as shown above.

The script

Let’s break it down line by line (mostly in homage to a great teacher, Randal L Schwartz).

 1 #!/usr/bin/env bash
 2
 3 readonly org="${1:?Specify org name}"
 4
 5 jqscript() {
 6
 7   cat << EOF
 8   .[]
 9   | [
10     .name,
11     "Name: \(.name)\n\nDescription: \(.description)\n\nLanguage: \(.language)\nWatchers: \(.watchers_count)\nStars: \(.stargazers_count)\nForks: \(.forks_count)"
12     ]
13   | @tsv
14 EOF
15
16 }
17
18 gh api \
19   "/orgs/$org/repos" \
20   --paginate \
21   --cache 1h \
22   --jq "$(jqscript)" \
23   | fzf \
24     --with-nth=1 \
25     --delimiter='\t' \
26     --preview='echo -e {2}' \
27     --preview-window=up:sharp:wrap:40%

1: the shebang uses env to find bash on my system to execute the contents of the file

3: the script expects a single argument to be specified – the name of the organisation on GitHub. For our purposes this should be SAP-samples

5-16: a simple function to encapsulate the small jq script that will be passed to the invocation of gh to parse the JSON output that is returned from the API call

8: the JSON output’s outermost element is an array, which means we start with .[] to say “take each of the array items”; each array item represents a repository within the organisation, and has different properties

9: we flow the array items (via the |) into a list of fields that we keep together with [ starting on this line, and ending with ] on line 12

10: the first field in the list is simply the value of the name property (the name of the repository)

11: the second field is a string that’s made up of literal and repository property values, combined into a multi-line string (note the newline characters in there \n); this string is what’s to be shown in the preview (at the top, in the demo above)

13: finally each list of fields is flowed into @tsv which produces a tab separated values set of records

18-22: the main action is in these lines – the call to gh‘s api facility

19: the API call is to the endpoint for listing organisation repositories – specifically for the organisation (in $org) specified when the script was invoked

20: there are a limited number of results returned by the API in any one response; the --paginate option tells gh to make enough calls to page through all of the results – very convenient!

21: the recent --cacheoption allows for cacheing of the results, to save on hitting the API endpoints too frequently and unnecessarily; it makes a lot of sense here given the frequency of new repository creations

22: the --jq option is also recent, and given that the API output is JSON, is very useful; we use the jq script defined earlier in the jqscript function here to produce that set of tab separated records (where the first field is the repository name and the second field is the multi-line string showing the repository details)

23: the (tab separated records) output is then passed into fzfto give us a chance to browse or search through the entire list and see the repositories’ details

24: using --with-nth=1 we can tell fzf to only show the first field in the actual selection list

25: we tell fzf how to know what the fields are with --delimiter='\t', i.e. the fields are separated by tab characters

26: with --preview='echo -e {2}' we tell fzf that we want to have something shown in a preview window for each item; what is shown is the result of echo -e {2} where {2} is an fzf placeholder representing the second field in the list (i.e. the multi-line string) and the -e switch tells echo to actually interpret backslash escapes, meaning that the newline characters (\n) in the field will be rendered properly and the preview will indeed be multi-line

27: the --preview-window=up:sharp:wrap:40% option tells fzf how to display the preview window, including that it should be at the top, above the list (up), that any long text lines should be wrapped (this is good for the value of the repositories’ description fields) and that the preview window should take up just less than half of the screen (40%)

And that’s it.

The command line is a powerful environment and with it come powerful tools that can help you retrieve, bend and shape the information you need to work with.

Trying it yourself

There’s a branch for this SAP Tech Bytes post in the accompanying SAP Tech Bytes repository, and it contains the version of the script org-sampler described above:

https://github.com/SAP-samples/sap-tech-bytes/tree/2021-04-05-exploring-sap-samples-with-gh-and-fzf

This post was inspired by Improving shell workflows with fzf.