Usage of golang syscall

Golang is a programming language with high development efficiency and strong concurrency performance. In order to better interact with the operating system, Golang introduces the syscall library. The syscall library provides a set of functions that encapsulate underlying system calls, allowing developers to more conveniently operate underlying system resources. This article will delve into the usage of the Golang syscall library.

1. Introduction of syscall library

In Golang, system calls generally use header files in C language, such as , < ;sys/stat.h> and other header files, but there is no corresponding header file in Golang. To solve this problem, Golang introduced the syscall library.

When using the syscall library in Golang, you need to import the "syscall" package in the code:

import (
    "syscall"
)

2. Basic usage of syscall

syscall library The functions directly correspond to the system call functions. For example, the open function corresponds to the Open function in syscall, the read function corresponds to the Read function in syscall, and so on. The naming rule for these functions is to capitalize the first letter of the original function name and remove the underscore. We can view all functions in syscall in Golang’s official documentation.

Take opening a file as an example to introduce the basic usage of syscall.

package main

import (
    "fmt"
    "syscall"
)

func main() {
    path := "test.txt"
    flag := syscall.O_RDWR | syscall.O_CREAT
    perm := syscall.S_IRUSR | syscall.S_IWUSR

    fd, err := syscall.Open(path, flag, perm)
    if err != nil {
        fmt.Printf("open file %s failed, err: %v", path, err)
        return
    }
    fmt.Printf("open file %s success, fd: %d", path, fd)
    syscall.Close(fd)
}

In the code, we first set the file path, the mode for opening the file, and the file permissions. Then, we open the file using the syscall.Open function, whose return value is the file descriptor. If opening the file fails, an error message is returned. Finally, we close the file using the syscall.Close function.

3. Comparison of syscall and os package

In Golang, another widely used system call library is the os package. The system call functions provided by the os package have many similarities with the functions in the syscall library, which makes many developers confused about their usage. Here, let’s compare how syscall and os packages are used to open files:

• Use syscall library:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    path := "test.txt"
    flag := syscall.O_RDWR | syscall.O_CREAT
    perm := syscall.S_IRUSR | syscall.S_IWUSR

    fd, err := syscall.Open(path, flag, perm)
    if err != nil {
        fmt.Printf("open file %s failed, err: %v", path, err)
        return
    }
    fmt.Printf("open file %s success, fd: %d", path, fd)
    syscall.Close(fd)
}

• Use os package:

package main

import (
    "fmt"
    "os"
)

func main() {
    path := "test.txt"

    file, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0644)
    if err != nil {
        fmt.Printf("open file %s failed, err: %v", path, err)
        return
    }
    defer file.Close()
    fmt.Printf("open file %s success", path)
}

Comparing the codes of the two, we can find that the OpenFile function in the os package provides file IO operations in a higher-level manner, and its parameters and return values ​​are also easier to understand. However, in some cases, using the os package may cause unnecessary overhead, because the functions in the os package often perform additional operations, such as formatting paths, verifying file permissions, and so on. In these cases, you can use the syscall library to directly call system-level functions, which can use operating system resources more efficiently. Therefore, the choice of using the syscall library or os package should be based on the application scenario.

4. Use the syscall library to read and write files

The syscall library provides two functions, Read and Write, for reading and writing files. Let's look at an example below, using the syscall library to read data from a file and print it to the console:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    path := "test.txt"
    flag := syscall.O_RDONLY

    fd, err := syscall.Open(path, flag, 0)
    if err != nil {
        fmt.Printf("open file %s failed, err: %v", path, err)
        return
    }
    defer syscall.Close(fd)

    buf := make([]byte, 1024)
    for {
        n, err := syscall.Read(fd, buf)
        if err != nil || n == 0 {
            break
        }
        fmt.Print(string(buf[:n]))
    }
}

In the code, we first open the file in read-only mode, and then use syscall.Read The function reads data from the file and prints the data to the console. It should be noted that we use the make function to declare a slice and use it as a read cache to store the data read by the syscall.Read function.

5. Summary

Through this article, we understand the basic usage of the syscall library and compare the similarities and differences between the syscall library and the os package. In actual development, we should flexibly choose the syscall library or os package according to different scenarios to meet the needs of the program. At the same time, we should also pay attention to the access restrictions of system call functions on underlying resources to avoid unnecessary permission access problems. By rationally using the syscall library, we can better operate the underlying system resources and improve the performance and robustness of the program.

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