Golang modifies file content

In the Go language, we can operate on files through the functions provided by the os package, including reading, writing and modifying files. Below I will introduce how to read and modify files respectively.

File reading

To read the file contents, we need to open the file and read it into memory. Here is a simple example of reading the file content:

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    // 打开文件
    data, err := ioutil.ReadFile("test.txt")
    if err != nil {
        fmt.Println(err)
        return
    }

    // 输出文件内容
    fmt.Println(string(data))
}

In the above code, we use the ioutil.ReadFile() function to read the file content and convert it into a string output. If an error occurs while reading the file, an error message will be output.

Modify the file

Modifying the file content is mainly divided into two steps: 1. Read the file content; 2. Modify the file content; 3. Rewrite the file. Next, we will describe these three steps in detail.

Read file content

Same as file reading, we use the ioutil.ReadFile() function to read file content. The following is the sample code:

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    // 打开文件
    data, err := ioutil.ReadFile("test.txt")
    if err != nil {
        fmt.Println(err)
        return
    }

    // 将文件内容转换成字符串
    content := string(data)

    // 输出文件内容
    fmt.Println(content)
}

In the code, we open a file named test.txt and use the ioutil.ReadFile() function to The content is read into the data variable. Next, we convert data into a string type in order to modify the file content.

Modify file content

After understanding the reading of file content, we need to modify the file next. To modify the file content, we need to convert it into a string type first and perform modification operations. The following is a simple example:

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    // 打开文件
    data, err := ioutil.ReadFile("test.txt")
    if err != nil {
        fmt.Println(err)
        return
    }

    // 将文件内容转换成字符串
    content := string(data)

    // 修改文件内容
    content = "hello, world!"

    // 输出修改后的内容
    fmt.Println(content)
}

In the above code, we modify the file by converting the file content into a string. In the code, we modify the file content to "hello, world!".

Rewrite the file

After completing the modification of the file content, we need to re-write the modified content to the file. For this we need to use the ioutil.WriteFile() function. The following is a sample code:

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    // 打开文件
    data, err := ioutil.ReadFile("test.txt")
    if err != nil {
        fmt.Println(err)
        return
    }

    // 将文件内容转换成字符串
    content := string(data)

    // 修改文件内容
    content = "hello, world!"

    // 重新写入文件
    err = ioutil.WriteFile("test.txt", []byte(content), 0644)
    if err != nil {
        fmt.Println(err)
        return
    }

    // 输出修改后的内容
    fmt.Println(content)
}

In the above code, we use the ioutil.WriteFile() function to write the modified file content to the file. This function accepts three parameters: file name, file content, and file permissions. Here we use the content variable as the file content and 0644 as the file permissions.

In this way, we have completed the modification of the file content. It should be noted that file modification operations should be done with caution to prevent data loss or irrecoverable damage.

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