Handle Files

Create a File

To create a file, you can use the os.Create function along with the defer statement to close the file after writing to it.

Example

run command

go run src/handle_files/create_file.go

package main

import (
    "fmt"
    "os"
)

func main() {
    file, err := os.Create("src/handle_files/example.txt")
    defer file.Close()
    if err != nil {
        fmt.Println(err)
        return
    }
}

Write into a File

Open the file in append mode and write to it using the os.OpenFile function.

Example

run command

go run src/handle_files/write_file.go

package main

import (
    "fmt"
    "os"
)

func main() {
    file, err := os.OpenFile("src/handle_files/example.txt", os.O_APPEND|os.O_WRONLY, 0644)
    if err != nil {
        fmt.Println(err)
        return
    }
    defer file.Close()

    size, err := file.WriteString("\nWriting a string into the file\n")
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println("Size written into file: ", size)
    _, err = file.Write([]byte("Using bytes to write"))
}

File Permission Number

In the os.OpenFile function, the perm argument is used to specify the file permission when creating or opening a file. It is an integer value that represents the file mode and permission bits. The typical file permission values used in Unix-like systems are represented in octal notation. The permission mode is composed of three digits, each of which represents the permissions for different user groups.

1. Owner Permissions: The first digit represents the permissions for the file owne.
2. Group Permissions: The second digit represents the permissions for the group that the file belongs to.
3. Other Permissions: The third digit represents the permissions for everyone else (other users).

The digits in the mode are a sum of permission bits:

1. 4: Read (r)
2. 2: Write (w)
3. 1: Execute (x)

And calculate the permissions numbers:

1. 6 (4 + 2) means read and write permissions (rw).
2. 4 (only 4) means read-only (r)..
3. 7 (4 + 2 + 1) means read, write, and execute permissions (rwx)..

Example

1. 0644: Owner has read and write (6), group and others have read-only (4).
2. 0755: Owner has read, write, and execute (7), group and others have read and execute (5).
3. 0600: Owner has read and write (6), no permissions for group and others.

Reading a File

To read from a file, you can use the os.Open function along with a Scanner from the bufio package.

Example

run command

go run src/handle_files/read_file.go

package main

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

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

    scanner := bufio.NewScanner(file)
    for scanner.Scan() {
        fmt.Println(scanner.Text())
    }
}

output

Writing a string into the file
Using bytes to write

Delete a File

To delete a file, you can use the os.Remove function.

Example

run command

go run src/handle_files/delete_file.go

package main

import (
    "fmt"
    "os"
)

func main() {
    err := os.Remove("src/handle_files/example.txt")
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println("File deleted successfully.")
}