How to use Linux system calls in Go?

With the continuous development of computer technology, our requirements for computer systems are getting higher and higher. In this process, the role of the operating system becomes increasingly important. Linux is a commonly used operating system, and its system calls have become a basic part of the Linux system. As a high-performance language for rapid development, the Go language naturally supports Linux system calls and provides a convenient underlying programming interface for the operating system.

This article will introduce how to use Linux system calls in Go language, and explain it in detail with relevant codes and examples.

1. Basics of Linux system calls

Linux system call refers to an interface provided in the Linux operating system for accessing the functions of the system kernel. Linux system calls can be seen as a way for user processes to make requests to the kernel. These requests may be to obtain specific information, perform certain specific operations, etc.

In Linux, the number of the system call is called the system call number. When using the system call, you need to pass the corresponding parameters. These parameters are instructions and data sent by the user process to the kernel. The return value of the system call is also placed in a special register and returned to the user process. System calls are implemented in Linux using soft interrupts, that is, by calling the int 0x80 instruction to achieve conversion from user mode to kernel mode.

2. System calls in Go language

The syscall library is used in Go language to implement system calls. This library encapsulates all system calls in the Linux system and provides a unified interface that programmers can use.

Commonly used system calls include:

1. Open file/directory: Open
2. Read file/directory content: Read
3. Write file /Directory content: Write
4. Close file/directory: Close
5. Delete file/directory: Remove

We take the above commonly used system calls as an example to describe how Using system calls in Go language.

1. Open a file/directory

To open a file/directory in Go language use the system call Open:

func Open(path string, flag int, perm uint32) (uintptr, error)

where path represents the open file/directory path; flag represents the operation flag, such as O_RDONLY represents read-only mode, O_WRONLY represents write-only mode, O_RDWR represents read-write mode, O_CREATE It means creating a file, etc.; perm means the permissions of the file/directory, such as 0777 means that the file can be read, written and executed. The return value of the Open function is a file descriptor of type uintptr and an error of type error.

The following is a sample code that demonstrates how to open a file and read the file content in Go language:

package main

import (
    "fmt"
    "os"
    "syscall"
)

func main() {
    filePath := "test.txt"
    fd, err := syscall.Open(filePath, syscall.O_RDONLY, 0)
    if err != nil {
        fmt.Println("Open file error:", err)
        return
    }
    defer syscall.Close(fd)

    fileInfo, err := os.Stat(filePath)
    if err != nil {
        fmt.Println("Get file info error:", err)
        return
    }

    fileSize := fileInfo.Size()
    buf := make([]byte, fileSize)

    n, err := syscall.Read(fd, buf)
    if err != nil {
        fmt.Println("Read file error:", err)
        return
    }

    fmt.Printf("Read %d bytes from file:
%s", n, string(buf))
}

2. Read file/directory content

The system call Read can be used to read the content from the file/directory. The sample code is as follows:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    fd, err := syscall.Open(".", syscall.O_RDONLY, 0)
    if err != nil {
        fmt.Println("Open directory error:", err)
        return
    }
    defer syscall.Close(fd)

    buf := make([]byte, 1024)

    // 循环遍历文件/目录中的内容
    for {
        n, err := syscall.Read(fd, buf)
        if err != nil {
            fmt.Println("Read directory error:", err)
            return
        }

        // 如果已经读取到文件/目录尾部，则退出循环
        if n == 0 {
            break
        }

        fmt.Printf("%d bytes:
%s", n, string(buf[:n]))
    }
}

3. Write the file/directory content

The system call Write can be used Write content to the file/directory. The sample code is as follows:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    filePath := "test.txt"
    fd, err := syscall.Open(filePath, syscall.O_RDWR|syscall.O_APPEND, 0)
    if err != nil {
        fmt.Println("Open file error:", err)
        return
    }
    defer syscall.Close(fd)

    content := "Hello, World!
"
    n, err := syscall.Write(fd, []byte(content))
    if err != nil {
        fmt.Println("Write file error:", err)
        return
    }

    fmt.Printf("Write %d bytes to file.
", n)
}

4. Close the file/directory

Use the system call Close to close an open file/directory. The sample code is as follows:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    fd, err := syscall.Open(".", syscall.O_RDONLY, 0)
    if err != nil {
        fmt.Println("Open directory error:", err)
        return
    }

    // 进行相关的操作

    syscall.Close(fd)
}

5. Delete files/directories

Use the system call Remove to delete files/directories. The sample code is as follows:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    filePath := "test.txt"
    err := syscall.Remove(filePath)
    if err != nil {
        fmt.Println("Remove file error:", err)
        return
    }

    fmt.Println("Remove file success.")
}

3. Summary

This article mainly talks about how to use Linux system calls in Go language. We introduced the basic knowledge of system calls, combined with commonly used system calls (Open, Read, Write, Close, Remove) to explain in detail, and gave relevant sample codes.

Through the study of this article, I believe that you have mastered the basic methods of using system calls in the Go language. I hope it will be helpful to you.

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