Write, append, read, and copy of golang files: examples of using bufio packages

golang Writing files 、 Additional 、 Read 、 Copy operation

Go Linguistic os There is a OpenFile function , The prototype is shown below ：

func OpenFile(name string, flag int, perm FileMode) (file *File, err error)

among name Is the file name of the file , If you are not running under the current path, you need to add a specific path ;flag Is the processing parameter of the file , by int type , The specific values may vary depending on the system , But the effect is the same .

Here are some common flag File processing parameters ：

• O_RDONLY： Open file in read-only mode ;
• O_WRONLY： Write only mode open file ;
• O_RDWR： Open file in read-write mode ;
• O_APPEND： Attach data to the end of the file when writing （ Additional ）;
• O_CREATE： If it doesn't exist, a new file will be created ;
• O_EXCL： and O_CREATE In combination with , The file must not exist , Otherwise an error is returned ;
• O_SYNC： When doing a series of write operations , Every time I have to wait for the last time I/O When the operation is finished, proceed ;
• O_TRUNC： If possible , Empty file on open .

【 Example 1】： Create a new file golang.txt, And write in it 5 sentence “http://c.biancheng.net/golang/”.

package mainimport (    "bufio"    "fmt"    "os")func main() {    // Create a new file , Write content  5  sentence  “http://c.biancheng.net/golang/”    filePath := "e:/code/golang.txt"    file, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE, 0666)    if err != nil {        fmt.Println(" File opening failure ", err)    }    // Shut down in time file Handle     defer file.Close()    // When writing a file , Use cached  *Writer    write := bufio.NewWriter(file)    for i := 0; i < 5; i++ {        write.WriteString("http://c.biancheng.net/golang/ \n")    }    //Flush Write the cached file to the file     write.Flush()}

After successful execution, a... Will be generated in the specified directory golang.txt file , Open the file as shown in the following figure ：

【 Example 2】： Open an existing file , Add content to the original content “C Chinese language network ”

package mainimport (    "bufio"    "fmt"    "os")func main() {    filePath := "e:/code/golang.txt"    file, err := os.OpenFile(filePath, os.O_WRONLY|os.O_APPEND, 0666)    if err != nil {        fmt.Println(" File opening failure ", err)    }    // Shut down in time file Handle     defer file.Close()    // When writing a file , Use cached  *Writer    write := bufio.NewWriter(file)    for i := 0; i < 5; i++ {        write.WriteString("C Chinese language network  \r\n")    }    //Flush Write the cached file to the file     write.Flush()}

After successful execution , open golang.txt The file discovery content was appended successfully , As shown in the figure below ：

【 Example 3】： Open an existing file , Read out the original content , Displayed on the terminal , And add 5 sentence “Hello,C Chinese language network ”.

package mainimport (    "bufio"    "fmt"    "io"    "os")func main() {    filePath := "e:/code/golang.txt"    file, err := os.OpenFile(filePath, os.O_RDWR|os.O_APPEND, 0666)    if err != nil {        fmt.Println(" File opening failure ", err)    }    // Shut down in time file Handle     defer file.Close()    // Read the contents of the original file , And it's displayed on the terminal     reader := bufio.NewReader(file)    for {        str, err := reader.ReadString('\n')        if err == io.EOF {            break        }        fmt.Print(str)    }    // When writing a file , Use cached  *Writer    write := bufio.NewWriter(file)    for i := 0; i < 5; i++ {        write.WriteString("Hello,C Chinese language network . \r\n")    }    //Flush Write the cached file to the file     write.Flush()}

After successful execution , The contents of the file will be printed on the console , And add the specified content to the file , As shown in the figure below ：

【 Example 4】： Write a program , Copy the contents of one file to another （ notes ： Both files already exist ）

package mainimport (    "fmt"    "io/ioutil")func main() {    file1Path := "e:/code/golang.txt"    file2Path := "e:/code/other.txt"    data, err := ioutil.ReadFile(file1Path)    if err != nil {        fmt.Printf(" File opening failure =%v\n", err)        return    }    err = ioutil.WriteFile(file2Path, data, 0666)    if err != nil {        fmt.Printf(" File opening failure =%v\n", err)    }}

After successful execution , The content found has been copied successfully , As shown in the figure below ：

Reference link ：

http://c.biancheng.net/view/5729.html