gen-posix: Atomic updates

2 files changed, 24 insertions, 6 deletions

diff --git a/Makefile b/Makefile
index 56f4be3..30107bb 100644
--- a/Makefile
+++ b/Makefile
@@ -38,7 +38,7 @@ public/imworkingon/imworkingon.css: public/imworkingon/imworkingon.scss
 
 public/posix/index.html: FORCE
 	mkdir -p $(@D)
-	go run ./cmd/gen-posix >$@
+	go run ./cmd/gen-posix
 
 # generate = checked in to Git #################################################
 
diff --git a/cmd/gen-posix/main.go b/cmd/gen-posix/main.go
index 66a2588..354fd3f 100644
--- a/cmd/gen-posix/main.go
+++ b/cmd/gen-posix/main.go
@@ -1,6 +1,8 @@
 package main
 
 import (
+	"bytes"
+	"fmt"
 	"html/template"
 	"os"
 )
@@ -179,12 +181,28 @@ var tmpl = `{{define "document"}}{{if .}}
 </html>
 `
 
-func main() {
-	err := template.Must(template.New("page").Parse(tmpl)).Execute(os.Stdout, map[string]interface{}{
+func mainWithError() error {
+	tmpl := template.Must(template.New("page").Parse(tmpl))
+
+	var out bytes.Buffer
+	if err := tmpl.Execute(&out, map[string]interface{}{
 		"Vendors":  Vendors,
 		"Editions": Editions,
-	})
-	if err != nil {
-		panic(err)
+	}); err != nil {
+		return err
+	}
+	if err := os.WriteFile("public/posix/index.new.html", out.Bytes(), 0666); err != nil {
+		return err
+	}
+	if err := os.Rename("public/posix/index.new.html", "public/posix/index.html"); err != nil {
+		return err
+	}
+	return nil
+}
+
+func main() {
+	if err := mainWithError(); err != nil {
+		fmt.Fprintf(os.Stderr, "%s: error: %v\n", os.Args[0], err)
+		os.Exit(1)
 	}
 }