add env command

.gitignore

@@ -1,3 +1,4 @@
 ,
 commago
 *~
+.env*

env.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+var commandEnvDescription = "load environment variable from .env file"
+
+func commandEnv(args []string) {
+	var flagSet = flag.NewFlagSet("env", flag.ContinueOnError)
+	envFilePath := flagSet.String("file", ".env", "the file contains environment variables to parse")
+	printToScreen := flagSet.Bool("print", false, "wethear or not print to screen")
+	_ = printToScreen
+	printWithExport := flagSet.Bool("export", false, "wethear or not add `export` prefix to each variable when printing")
+	flagSet.Parse(args[1:])
+	_, err := parseEnvFileAndSetEnv(*envFilePath, *printToScreen, *printWithExport)
+	if err != nil {
+		fmt.Printf("%v", err)
+		os.Exit(2)
+	}
+	if len(flagSet.Args()) > 0 {
+		cmd := exec.Command(flagSet.Args()[0], flagSet.Args()[1:]...)
+		var out strings.Builder
+		cmd.Stdout = &out
+		err = cmd.Run()
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf(out.String())
+	}
+
+}
+
+func parseEnvFileAndSetEnv(filePath string, printToScreen, printWithExport bool) (string, error) {
+	raw, err := os.ReadFile(filePath)
+	if err != nil {
+		return "", fmt.Errorf("read from %v has error: %w", filePath, err)
+	}
+	rawLines := strings.Split(string(raw), "\n")
+	for i, line := range rawLines {
+		trimedLine := strings.TrimSpace(line)
+		if strings.HasPrefix(trimedLine, "#") {
+			continue
+		}
+		if trimedLine == "" {
+			continue
+		}
+		parts := strings.Split(trimedLine, "=")
+		if len(parts) != 2 {
+			return "", fmt.Errorf("line %v is malformed: `%v`", i+1, trimedLine)
+		}
+		if strings.TrimSpace(parts[0]) != parts[0] {
+			return "", fmt.Errorf("line %v is malformed: between variable name and `=` can't has any space", i+1)
+		}
+		if strings.TrimSpace(parts[1]) != parts[1] {
+			return "", fmt.Errorf("line %v is malformed: between `=` and value can't has any space", i+1)
+		}
+		os.Setenv(parts[0], parts[1])
+		if printToScreen {
+			s := fmt.Sprintf("%v=%v\n", parts[0], parts[1])
+			if printWithExport {
+				s = fmt.Sprintf("export %v", s)
+			}
+			fmt.Print(s)
+		}
+
+	}
+	return "", nil
+}

main.go

@@ -8,15 +8,18 @@ import (
 func commandsUsage() string {
 	return fmt.Sprintf(
 		`commands:
+  env         %v
   path        %v
   time        %v
   week        %v
-`, commandPathDescription, commandTimeDescription, commandWeekDescription)
+`, commandEnvDescription, commandPathDescription, commandTimeDescription, commandWeekDescription)
 }
 
 func main() {
 	if len(os.Args) >= 2 {
 		switch os.Args[1] {
+		case "env":
+			commandEnv(os.Args[1:])
 		case "path":
 			commandPath(os.Args[1:])
 		case "time":