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Golang program to open a file in read-only mode

Here, we are going to learn how to open a file in read-only mode in Golang (Go Language)?
Submitted by Nidhi, on April 05, 2021 [Last updated : March 04, 2023]

How to open a file in read-only mode in Golang?

Problem Solution:

In this program, we will open a file in read-only mode using os.Open() function.

Program/Source Code:

The source code to open a file in read-only mode is given below. The given program is compiled and executed successfully.

Golang code to open a file in read-only mode

// Golang program to open a file in read-only mode

package main

import "os"
import "fmt"

func main() {
	Myfile, err := os.Open("Sample.txt")
	if err != nil {
		fmt.Println("Unable to open file")
	}

	len, err := Myfile.WriteString("Hello World")

	if len == 0 {
		fmt.Printf("File is opened in read-only mode")
	} else {
		fmt.Printf("%d characters written into file", len)
	}

	Myfile.Close()
}

Output:

File is opened in read-only mode

Explanation:

In the above program, we declare the package main. The main package is used to tell the Go language compiler that the package must be compiled and produced the executable file. Here, we imported the fmt, os packages then we can use a function related to the fmt and os package.

In the main() function, we opened the "Sample.txt" file in read-only mode using os.Open() function. Then we tried to write content into the file but we are unable to write data into the file because the file is opened in read-only mode. After that, we printed the appropriate message on the console screen.

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