Initial commit

README.md

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+# envconf
+
+It's simple env based config file transform for docker boot time configuration.
+
+
+```
+$cat a.conf
+[servera]
+HOST={{ .HOST | default "B" }}
+
+$export HOST="HOSTA"
+
+$envconf a.conf
+
+$cat a.conf
+```
+
+``` 
+$envconf a.conf b.conf ...
+or
+$export ENV_CONF_FILES=a.conf:b.conf:c.conf
+$envconf
+```
+
+
+
+
+

main.go

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+package main
+
+import (
+	"github.com/namsral/flag"
+	"log"
+	"os"
+	"strings"
+	"text/template"
+)
+
+const (
+	CONF_FILES = "ENV_CONF_FILES"
+)
+
+var (
+	env             map[string]string = make(map[string]string)
+	confPaths       []string
+	templateFuncMap template.FuncMap
+)
+
+func init() {
+	flag.Parse()
+
+	if len(flag.Args()) >= 0 {
+		for _, path := range flag.Args() {
+			confPaths = append(confPaths, path)
+		}
+	}
+
+	for _, pair := range os.Environ() {
+		item := strings.SplitN(pair, "=", 2)
+		if len(item) < 2 {
+			log.Fatalf("invalid item from os.Environ %s", pair)
+		}
+		env[item[0]] = item[1]
+	}
+
+	if val, ok := env[CONF_FILES]; ok {
+		paths := strings.Split(val, ":")
+		for _, path := range paths {
+			confPaths = append(confPaths, path)
+		}
+	}
+
+	templateFuncMap = template.FuncMap{
+		"default": func(args ...string) string {
+			return args[0]
+		},
+	}
+}
+
+func main() {
+	for _, path := range confPaths {
+		err := transformFile(path)
+		if err != nil {
+			log.Printf("Err: %s,%s", path, err)
+		} else {
+			log.Printf("Transformed %s", path)
+		}
+	}
+}
+
+func transformFile(path string) error {
+	t := template.New(path)
+	t = t.Funcs(templateFuncMap)
+	t, err := t.ParseFiles(path)
+	if err != nil {
+		log.Printf("Err: Parsing file %s %s", path, err)
+		return err
+	}
+
+	t = t.Funcs(templateFuncMap)
+
+	file, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		log.Printf("Err: Can't open a file %s %s", path, err)
+		return err
+	}
+	defer func() {
+		if file != nil {
+			file.Close()
+		}
+	}()
+
+	if err = t.Execute(file, env); err != nil {
+		return err
+	}
+
+	return nil
+}