teocci · January 10, 2025 20:00 · Nov 3, 2021 · Nov 3, 2021 · Nov 3, 2021
diff --git a/abstact.md b/abstact.md
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+## Handling Unix Signals In Golang
+Unix signals are software interrupts that are sent to a program to indicate that some important event has occurred. The events can vary from user requests to illegal memory access errors. Some signals, such as the interrupt signal, indicate that a user has asked the program to do something, not in the usual control flow.
+
+Dealing with the operating system signals is important for various use cases in applications. For example, we might want a server to gracefully shut down when it receives a SIGTERM, or a command-line tool to stop processing input if it receives a SIGINT. Here’s how to handle signals in Go with channels.
+
+### os/signal package
+Golang’s os/signal the package allows you to configure the behavior of your Golang program upon receiving certain types of UNIX signals. Most Linux/Unix-based programs will gladly die upon receiving a kill signal, but in case you want your program to intercept the signal first, perform some backup, flush data to disk, etc before dying, then you should use the os/signal package.
+
+### Types of signals
+We are going to focus on asynchronous signals. They are not triggered by program errors but are instead sent from the kernel or from some other program.
+* SIGHUP the signal is sent when a program loses its controlling terminal
+* SIGINT the signal is sent when the user at the controlling terminal presses the interrupt character, which by default is ^C (Control-C)
+* SIGQUIT the signal is sent when the user at the controlling terminal presses the quit character, which by default is ^\ (Control-Backslash)
+* SIGTERM the signal is a generic signal used to cause program termination
+Here is a simple Golang example on how to intercept the most common UNIX kill/terminate signals.
+Note: Please read code comments for better understanding.
+
+Run the above program by copying it on your local machine. I run my program with the name signal-controller. go. Following are the steps and my observations when I execute this on my Ubuntu machine.
+
+Terminal 1
+```bash
+go build signal-controller.go
+./signal-controller
+```
+Get the PID of running binary in this example: 451575
+
+Terminal 2:
+```bash
+kill -SIGINT 451575
+# Terminal 1 - Output - "Signal interrupt triggered."
+
+kill -SIGHUP 451575
+# Terminal 1 - Output - "Signal hang up triggered."
+
+kill -SIGTERM 451575
+# Terminal 1 - Output - "Signal terminte triggered."
+
+kill -SIGQUIT 451575
+#Terminal 1 - Output - "Signal quit triggered."
+```
+### Conclusion
+Unix signal can be easily handled in Golang by using the os/signalpackage. We need to use a channel of type os.Signalto read signals. You can implement code to handle every type of Unix signal received by the program.
diff --git a/handle-os-signals.go b/handle-os-signals.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func main() {
+	signal_chan := make(chan os.Signal, 1)
+	signal.Notify(signal_chan,
+		syscall.SIGHUP,
+		syscall.SIGINT,
+		syscall.SIGTERM,
+		syscall.SIGQUIT)
+
+	exit_chan := make(chan int)
+	go func() {
+		for {
+			s := <-signal_chan
+			switch s {
+			// kill -SIGHUP XXXX
+			case syscall.SIGHUP:
+				fmt.Println("hungup")
+
+			// kill -SIGINT XXXX or Ctrl+c
+			case syscall.SIGINT:
+				fmt.Println("Warikomi")
+
+			// kill -SIGTERM XXXX
+			case syscall.SIGTERM:
+				fmt.Println("force stop")
+				exit_chan <- 0
+
+			// kill -SIGQUIT XXXX
+			case syscall.SIGQUIT:
+				fmt.Println("stop and core dump")
+				exit_chan <- 0
+
+			default:
+				fmt.Println("Unknown signal.")
+				exit_chan <- 1
+			}
+		}
+	}()
+
+	code := <-exit_chan
+	os.Exit(code)
+}