Golang如何读取和写入文件 Golang文件操作的常见场景与代码示例

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    file, err := os.Open("example.txt")
    if err != nil {
        fmt.Println("Error opening file:", err)
        return
    }
    defer file.Close()

    reader := bufio.NewReader(file)
    scanner := bufio.NewScanner(reader) // Or just use bufio.NewScanner(file) directly

    for scanner.Scan() {
        line := scanner.Text()
        fmt.Println(line)
    }

    if err := scanner.Err(); err != nil {
        fmt.Println("Error reading file:", err)
    }
}

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    file, err := os.Create("output.txt")
    if err != nil {
        fmt.Println("Error creating file:", err)
        return
    }
    defer file.Close()

    writer := bufio.NewWriter(file)
    defer writer.Flush() // 确保所有缓冲数据都写入文件

    _, err = writer.WriteString("Hello, world!\n")
    if err != nil {
        fmt.Println("Error writing to file:", err)
        return
    }

    _, err = writer.WriteString("This is another line.\n")
    if err != nil {
        fmt.Println("Error writing to file:", err)
        return
    }

    fmt.Println("Data written to file successfully.")
}

package main

import (
    "fmt"
    "os"
)

func main() {
    // 创建文件，并指定权限为 0644
    file, err := os.OpenFile("permissions.txt", os.O_CREATE|os.O_WRONLY, 0644)
    if err != nil {
        fmt.Println("Error creating file:", err)
        return
    }
    defer file.Close()

    _, err = file.WriteString("This file has specific permissions.\n")
    if err != nil {
        fmt.Println("Error writing to file:", err)
        return
    }

    fmt.Println("File created with specific permissions.")

    // 尝试修改文件权限
    err = os.Chmod("permissions.txt", 0755)
    if err != nil {
        fmt.Println("Error changing permissions:", err) // 可能会返回权限错误
        // 注意：如果当前用户没有权限修改文件，这里会报错
    } else {
        fmt.Println("File permissions changed successfully.")
    }
}

package main

import (
    "fmt"
    "io"
    "os"
)

func main() {
    sourceFile := "large_file.txt"
    destinationFile := "large_file_copy.txt"

    source, err := os.Open(sourceFile)
    if err != nil {
        fmt.Println("Error opening source file:", err)
        return
    }
    defer source.Close()

    destination, err := os.Create(destinationFile)
    if err != nil {
        fmt.Println("Error creating destination file:", err)
        return
    }
    defer destination.Close()

    bytesCopied, err := io.Copy(destination, source)
    if err != nil {
        fmt.Println("Error copying file:", err)
        return
    }

    fmt.Printf("File copied successfully. Bytes copied: %d\n", bytesCopied)
}

package main

import (
    "fmt"
    "os"
)

func main() {
    filename := "myfile.txt"

    _, err := os.Stat(filename)
    if os.IsNotExist(err) {
        fmt.Println("File does not exist.")
    } else if err != nil {
        fmt.Println("Error checking file:", err)
    } else {
        fmt.Println("File exists.")
    }
}

package main

import (
    "errors"
    "fmt"
    "os"
)

func main() {
    file, err := os.Open("nonexistent.txt")
    if err != nil {
        if errors.Is(err, os.ErrNotExist) {
            fmt.Println("File does not exist.")
        } else if errors.Is(err, os.ErrPermission) {
            fmt.Println("Permission denied.")
        } else {
            fmt.Println("Error opening file:", err)
        }
        return
    }
    defer file.Close()

    // ...
}