From d63a7bf71f0f6260032d07399dae3f141ee6de83 Mon Sep 17 00:00:00 2001
From: Patrick Spek <p.spek@tyil.nl>
Date: Mon, 3 Apr 2023 09:40:35 +0200
Subject: Add blog post on templating

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 .../2023/2023-03-26-finally-templating-bashtard.md | 86 ++++++++++++++++++++++
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+---
+date: 2023-03-29
+title: Finally, Templating in Bashtard!
+tags:
+- Bash
+- Bashtard
+- FreeBSD
+- GNU+Linux
+---
+
+In the past year, I've written Bashtard, a simple configuration system written
+in Bash to minimize the required dependencies, and to have a better system to
+handle different distributions/OSs in your cluster. Especially the past two
+months I've done quite a bit of work on it. I've worked out how to do reusable
+playbooks, generate a usable Debian package from the Makefile, extend the
+supported platforms, and more. And now, I've finally found a library to improve
+templating functionality, [Bash Pure Template](https://github.com/husixu1/bpt).
+
+When I originally started Bashtard I had looked around for nice and simple
+templating solutions that I could use. Sadly, pretty much all the available
+results required me to add dependencies, or couldn't really do more than what I
+did using `sed` and `awk`.
+
+For a long time, I had accepted that the kind of system that I wanted didn't
+exist, and I wasn't interested in making it myself at the time. Last night,
+however, I decided to just give it a quick search to see if anything had
+changed, and BPT popped up somewhere in my results. Having a quick look through
+the documentation made me very interested, it seemed to have all the features I
+desired, while still sticking to utilities I've already accepted for Bashtard.
+
+With one small exception, `md5sum`. This utility is not available on the FreeBSD
+systems I maintain. On FreeBSD, this tool is called `md5`, and has different
+options it can use. On the bright side, both `md5sum` and `md5` accept the
+content to be hashed on `STDIN`, and will write the hash to `STDOUT`.
+Additionally, Bashtard already contains logic to deduce what kind of system it
+is running on.
+
+And so I decided it's worth a try. There's only 5 references to `md5sum`, and
+the all happen in the same function, `bpt.fingerprint`. I've added an extra
+variable, `util`, and a `case...esac` to set this variable.
+
+```bash
+local util
+
+case "${BASHTARD_PLATFORM[key]}" in
+    freebsd) util=md5 ;;
+    linux-*) util=md5sum ;;
+    *)
+        debug "bpt/fingerprint" "Falling back to md5sum for hashing"
+        util=md5sum
+        ;;
+esac
+```
+
+After that, just replace all the `md5sum` invocations with `"$util"`. And a
+quick test later, it seems to function just fine. Implementing BPT as a library
+was incredibly straightforward too.
+
+```bash
+. "$BASHTARD_LIBDIR/vendor/bpt.bash"
+
+file_template_bpt()
+{
+    local file
+
+    file="$1" ; shift
+
+    eval "$* bpt.main ge \"$file\""
+}
+```
+
+The `eval` is a bit icky, but it saves me from polluting the environment
+variables through various `export`s.
+
+Another small adjustment I've made to BPT is the shebang. Upstream uses
+`#!/bin/bash`, but this is incorrect on some systems, including FreeBSD. It uses
+`#!/usr/bin/env bash` in the Bashtard version. Additionally, the upstream
+repository uses `.sh` as the file extension, which I've updated to be `.bash` to
+more accurately reflect which shell it is used with. Upstream also uses a
+4-space indent, which I've left as-is for now, since indentation is more of a
+personal choice, even if that choice is wrong. Finally, I added 3 `shellcheck
+disable` rules to make shellcheck happy.
+
+After some playbook testing on my own systems, I can say that BPT works pretty
+well so far, and I'm very glad the author made it available as free software.
+Thanks!
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