go fmt readme snippets and shellcheck check script

.github/workflows/shell.yml

@@ -0,0 +1,27 @@
+name: Shell
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  bash:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Prepare
+      run: |
+        sudo apt-get update -y
+        sudo apt-get install shellcheck
+        mkdir -p ~/.local/bin/
+        wget -O ~/.local/bin/shfmt https://github.com/mvdan/sh/releases/download/v3.8.0/shfmt_v3.8.0_linux_amd64
+        chmod +x ~/.local/bin/shfmt
+
+    - name: Shellcheck
+      run: find . -type f -name '*.sh' -print0 | xargs -0 shellcheck
+    - name: Shell format (shfmt)
+      run: find . -type f -name '*.sh' -print0 | xargs -0 shfmt -d
+

scripts/compile_readme_snippets.sh

@@ -4,15 +4,19 @@ mkdir -p tmp
 awk '/^```go$/ {p=1}; p; /^```$/ {p=0;print"--- --- ---"}' README.md |
 	grep -vE '^```(go)?$' |
 	csplit \
-		-z -s -\
+		-z -s - '/--- --- ---/' \
-		'/--- --- ---/' \
 		'{*}' \
 		--suppress-matched \
 		-f tmp/readme_snippet_ -b '%02d.go'
 
-for snippet in ./tmp/readme_snippet_*.go
+for snippet in ./tmp/readme_snippet_*.go; do
-do
 	echo "building $snippet ..."
-	go build -v "$snippet" || exit 1
+	go build -v -o tmp/tmp "$snippet" || exit 1
 done
 
+for snippet in ./tmp/readme_snippet_*.go; do
+	echo "checking format $snippet ..."
+	if ! diff -u <(echo -n) <(gofmt -d "$snippet"); then
+		exit 1
+	fi
+done