How to use golang signal method

Signal in Golang is an inter-process communication mechanism. It can be used for inter-process communication, as well as handling abnormal signals in the program or closing the program. In Golang, signal processing is by monitoring the signal and processing the captured signal. Golang provides the signal package to process signals. Through the signal package, we can customize, ignore, and process the captured signals. This article will introduce the signal package in Golang and how to use it to handle signals.

Part 1: Introduction to the signal package

The signal package is a package used to process signals in Golang. It provides operations such as registration, processing and triggering of process signals. The most important function in the signal package is signal.Notify(). Through this function, you can monitor multiple signals and specify the function to be executed after the signal is triggered.

The following are some common functions and types in the signal package:

type Signal

type NotifyFunc func(os.Signal)

func Notify(c chan<- os.Signal, sig ...os.Signal)
func Stop(c chan<- os.Signal)
func Reset(sig ...os.Signal)

Among them, the Signal type defines the type of signal, the NotifyFunc type defines the function to be executed when the signal arrives, and the Notify function Used to listen for signals from the operating system. The Stop function is used to stop registering notification receivers for the c channel. After calling the Stop function, call the Notify function again to re-register the receiver. The Reset function is used to restore the default behavior of a signal to its default value.

Part 2: How to use the signal package

The following will introduce how to use the signal package to monitor, process and trigger signals in Golang.

The sample code is as follows:

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
)

func main() {
    // 创建一个接收信号的通道
    sigs := make(chan os.Signal, 1)

    // 注册信号
    signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)

    // 等待信号
    fmt.Println("等待信号：")
    sig := <-sigs
    fmt.Println("收到信号：", sig)
}

In the above code, we create a channel sigs to receive signals, use the signal.Notify function to add the SIGINT and SIGTERM signals to the channel, and then wait The arrival of these signals. When any of these signals arrives, the program reads the signal from the channel and prints it.

We can use the kill command to send a signal to the program, as follows:

$ kill -s SIGINT PID

where PID is the process ID of the program. After executing the above command, the program will read the SIGINT signal from the channel that receives the signal and output the received signal. If we want to listen to more signals and perform other operations when the signal is triggered, we can consider using the NotifyFunc type callback function provided by the signal package.

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
)

func main() {
    // 创建一个接收信号的通道
    sigs := make(chan os.Signal, 1)

    // 注册信号，并指定信号触发时要执行的操作
    signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM, os.Interrupt)
    go func() {
        // 等待信号，并输出信号信息
        sig := <-sigs
        fmt.Println("收到信号：", sig)
        os.Exit(0)
    }()

    // 主程序继续执行
    for {
        fmt.Println("正在运行……")
    }
}

In the above code, we use an anonymous function to listen for the signal, output the signal information when the signal arrives, and call the os.Exit function to close the process. We added an infinite loop to the program so that the program will continue to execute until it exits after receiving the signal.

Part 3: Optimized use of signal package

In practical applications, programs are often required to perform some specific operations after receiving certain signals. Common ones include program exit, Release resources, etc. In order to better cope with these needs, we can optimize our program by adding custom processing functions.

For example, we can customize a function. When the program receives the SIGTERM signal, it will call this function to release the resources occupied by the program and exit the program.

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
)

func main() {
    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)

    go func() {
        <-c
        cleanup()
        os.Exit(0)
    }()

    for {
        fmt.Println("正在运行……")
    }
}

func cleanup() {
    fmt.Println("程序正在关闭……")
    // 释放占用的资源等
}

In the above example, we defined a cleanup function, which will be executed when receiving the SIGTERM or Ctrl C signal. The program will first output "The program is closing..." and perform some cleaning operations. , and then the program will exit normally.

Part 4: Summary

The signal package in Golang provides a convenient signal processing mechanism, which can be used to monitor signals from the system in the program and perform corresponding operations, such as the program Exit, release resources, etc. When using the signal package, we can customize the processing function to handle the signal and exit the program urgently. In addition, we also need to pay attention to the special properties of some signals and choose processing methods according to needs. In practical applications, we need to use signals more carefully to avoid security issues caused by improper signal processing.

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