Published on

Golang: Reading from Files and Writing to Disk with Golang


Today we will create a very basic application to read content from a file, and write the content from the file back to disk, but to another filename.

Basically, doing a copy of the file to another filename.

Golang Environment: Golang Docker Image

Dropping into a Golang Environment using Docker:

$ docker run -it golang:alpine sh

Our Golang Application

After we are in our container, lets write our app:

package main

import (

func main() {

    content, error := ioutil.ReadFile("source-data.txt")
    if error != nil {

    error = ioutil.WriteFile("destination-data.txt", content, 0644)
    if error != nil {

Building our application to a binary:

$ go build app.go

Creating our source-data.txt :

$ echo "foo" > source-data.txt

Running the Golang App:

When we run this app, it will read the content of source-data.txt and write it to destination-data.txt:

$ ./app.go

We can see that the file has been written to disk:

$ ls | grep data

Making sure the data is the same, we can do a md5sum hash function on them:

md5sum source-data.txt
# d3b07384d113edec49eaa6238ad5ff00  source-data.txt


md5sum destination-data.txt
# d3b07384d113edec49eaa6238ad5ff00  destination-data.txt


This was a very static way of doing it, as you need to hardcode the filenames. In the next post I will show how to use arguments to make it more dynamic.

Thank You

Thanks for reading, feel free to check out my website, and subscrube to my newsletter or follow me at @ruanbekker on Twitter.

Buy Me A Coffee