Merge pull request #836 from devlights/add-unix-forkjoin-example

Author: devlights

examples/singleapp/unix/forkjoin/02.join/.gitignore

@@ -0,0 +1 @@
+app

examples/singleapp/unix/forkjoin/02.join/Taskfile.yml

@@ -0,0 +1,18 @@
+# https://taskfile.dev
+
+version: '3'
+
+vars:
+  APP_NAME: app
+
+tasks:
+  default:
+    cmds:
+      - task: run
+  build:
+    cmds:
+      - go build -o {{.APP_NAME}}{{.exeExt}}
+  run:
+    deps: [ build ]
+    cmds:
+      - ./{{.APP_NAME}}{{.exeExt}}

examples/singleapp/unix/forkjoin/02.join/main.go

@@ -0,0 +1,96 @@
+//go:build linux
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+var (
+	gi int
+)
+
+func init() {
+	log.SetFlags(0)
+}
+
+func main() {
+	if err := run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func run() error {
+	os.Stdout.Sync()
+	os.Stderr.Sync()
+
+	var li int
+
+	//
+	// Fork
+	//
+	pid, _, errno := unix.RawSyscall(unix.SYS_FORK, 0, 0, 0)
+	if errno != 0 {
+		return fmt.Errorf("fork failed: %d", errno)
+	}
+
+	var err error
+	switch pid {
+	case 0:
+		err = child(pid, &li)
+	default:
+		err = parent(pid)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	log.Printf("[%5d] li = %d, gi = %d", pid, li, gi)
+
+	return nil
+}
+
+func child(pid uintptr, i *int) error {
+	log.Printf("[%5d] This is the child process.", pid)
+
+	for range 3 {
+		log.Printf("[%5d] child processing...", pid)
+		*i++
+		gi++
+		time.Sleep(time.Second)
+	}
+
+	return nil
+}
+
+func parent(pid uintptr) error {
+	log.Printf("[%5d] This is the parent process.", pid)
+
+	//
+	// Join
+	//
+	log.Printf("[%5d] parent process WAIT started.", pid)
+	defer log.Printf("[%5d] parent process WAIT done.", pid)
+
+	var status unix.WaitStatus
+	if _, err := unix.Wait4(int(pid), &status, 0, nil); err != nil {
+		return fmt.Errorf("wait() failed: %w", err)
+	}
+
+	//
+	// WIFEXITED(status) と等価
+	//
+	if status.Exited() {
+		log.Printf("[%5d] Child process exited with status: %d", pid, status.ExitStatus())
+	} else {
+		log.Printf("[%5d] Child process did not exit normally: %d", pid, status.ExitStatus())
+	}
+
+	return nil
+}