Initial commit.

Author: gamemann

.gitignore

@@ -0,0 +1,2 @@
+loader
+test

Makefile

@@ -0,0 +1,5 @@
+all:
+	go build loader.go
+	go build test.go
+.PHONY: all
+.DEFAULT: all

README.md

@@ -0,0 +1,23 @@
+# Go Spawn & Debug Process
+This is a small project to demonstrate how to spawn multiple processes from a Go program and have the Go program write their `stdout` and `stderr` lines to a log file.
+
+In this example, we have `test` and `loader` Go programs.
+
+The `test` program outputs a random string from the `messages` variable each second to `stdout`. This is just used as a demo program.
+
+The `loader` program runs the `test` program five times and outputs their `stdout` and `stderr` pipes to a log file in the `logs/` directory (e.g. `logs/<pid>.log`).
+
+## Building
+You may use `make` via Makefile to build everything easily. Otherwise, you may use `go build loader.go` and `go build test.go` to build the Go programs.
+
+## Running
+Simply run the `loader` executable to test.
+
+```bash
+./loader
+```
+
+**Note** - The `remove_logs.sh` file is ran on each loader start. This Bash script simply removes all log files in the `logs/` directory so we start off from a clean slate and the loader ignores any errors from executing the file.
+
+## Credits
+* [Christian Deacon](https://github.com/gamemann)

loader.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/signal"
+	"syscall"
+)
+
+type TestProcess struct {
+	Process *exec.Cmd
+	Stdout  *bufio.Writer
+	Stderr  *bufio.Writer
+}
+
+const RMLOGS_EXEC = "./remove_logs.sh"
+const EXEC = "./test"
+const NUM_PROCESSES = 5
+
+func main() {
+	// Remove logs by using shell script.
+	rmLogs := exec.Command(RMLOGS_EXEC)
+
+	err := rmLogs.Run()
+
+	if err != nil {
+		fmt.Println("Failed to remove logs via shell script.")
+		fmt.Println(err)
+	}
+
+	var processes []*TestProcess
+
+	for i := 0; i < NUM_PROCESSES; i++ {
+		process := exec.Command(EXEC)
+
+		stdoutPipe, _ := process.StdoutPipe()
+		stderrPipe, _ := process.StderrPipe()
+
+		err := process.Start()
+
+		if err != nil {
+			fmt.Printf("[%d] Error creating process.\n", i)
+			fmt.Println(err)
+
+			continue
+		}
+
+		if process.Process == nil {
+			fmt.Printf("[%d] Could not find process.\n", process.Process.Pid)
+
+			continue
+		}
+
+		// Create log file.
+		fileName := fmt.Sprintf("logs/%d.log", process.Process.Pid)
+		logFile, err := os.Create(fileName)
+
+		if err != nil {
+			fmt.Printf("[%d] Error creating log file :: %s.\n", process.Process.Pid, fileName)
+
+			continue
+		}
+
+		stdoutWriter := bufio.NewWriter(logFile)
+		stderrWriter := bufio.NewWriter(logFile)
+
+		// Create goroutines to capture stdout and stderr output and write them our log files.
+		go func() {
+			scanner := bufio.NewScanner(stdoutPipe)
+			for scanner.Scan() {
+				line := scanner.Text()
+				stdoutWriter.WriteString(line + "\n")
+				stdoutWriter.Flush()
+			}
+		}()
+
+		go func() {
+			scanner := bufio.NewScanner(stderrPipe)
+			for scanner.Scan() {
+				line := scanner.Text()
+				stderrWriter.WriteString(line + "\n")
+				stderrWriter.Flush()
+			}
+		}()
+
+		processes = append(processes, &TestProcess{Process: process, Stdout: stdoutWriter, Stderr: stderrWriter})
+	}
+
+	fmt.Println("Started loader. Check logs/ directory for outputs.")
+
+	sigc := make(chan os.Signal, 1)
+	signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
+
+	<-sigc
+
+	os.Exit(0)
+}

logs/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

remove_logs.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+rm -f logs/*.log

test.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+)
+
+var messages = []string{
+	"This is a test message",
+	"Another test message.",
+	"Or ANOTHER test message.",
+	"Or yet ANOTHER test message!!!!",
+}
+
+func Repeat() {
+	for range time.Tick(time.Second * 1) {
+		fmt.Println(messages[rand.Intn(len(messages))])
+	}
+}
+
+func main() {
+	// Repeat.
+	go Repeat()
+
+	sigc := make(chan os.Signal, 1)
+	signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
+
+	<-sigc
+
+	os.Exit(0)
+}