Golang Working With Files...

#go #cli #beginners

Today a short one again. I have played around with some go again and wanted to write it down. There are multiple options to some of the stuff i did. So this is not a comprehensive guide.

Check if file exists

func fileExists(fileName string) (bool, error) {
    info, err := os.Stat(fileName)
    if err != nil {
        if os.IsNotExist(err) {
            return false, nil
        } else {
            return false, err
        }
    }
    return !info.IsDir(), nil
}

Create a file and write text to it

created, err = os.Create("test.txt")
if err != nil {
    log.Fatal(err)
}

//write to text file
//i ignore the number of bytes writen here
_, err = created.WriteString("Hello World")
if err != nil {
    log.Fatal(err)
}

//Close the file so it can be used later
created.Close()

Learned a lesson here. In my first version i wrote defer created.close(). But than later ran into problems, when i wanted to read from the file. So you need to close the file if you want to read from it in the same function.

Delete a file

created, err = os.Create("toDelete.txt")
if err != nil {
   log.Fatal(err)
}
created.Close()

err := os.Remove("toDelete.txt")
if err != nil {
   log.Fatal(e)
}

Read from a text file - 1

anotherFile, err := os.Open("anotherFile.txt")
if err != nil {
    log.Fatal(err)
}
scanner := bufio.NewScanner(anotherFile)
for scanner.Scan() {
    fmt.Println(scanner.Text())
}

if err := scanner.Err(); err != nil {
    log.Fatal(err)
}

Read from a text file - 2

content, err := os.ReadFile(fileName)

if err != nil {
    log.Fatal(err)
}
//The content is a []byte because of that: string(...)
fmt.Println(string(content))
}

Not much to adress here. I slowy see the verbosity of go. Haven't made up my mind about the language yet.

Copy or move a file

//copy a file
bytesRead, err := ioutil.ReadFile("fileToCopy.txt")
if err != nil {
    log.Fatal(err)
}
ioutil.WriteFile("cptrgt/CopyTarget.txt", bytesRead, os.ModePerm)

//Move a file
err = os.Rename("oldFile.txt", "cptrgt/newFile.txt")
if err != nil {
    log.Fatal(err)
}

Don't like how to move a file. Not a catastrophe but also not really intuitive either. Have not tested the copy speeds yet.

Create and recursivly delete a Folder

//create a new Folder
if err := os.Mkdir("cptrgt", os.ModePerm); err != nil {
    log.Fatal(err)
}

//delete a folder recursively
err := os.RemoveAll("cptrgt")
if err != nil {
    log.Fatal(err)
}

After my last post i was happy a about the syntax but now i stumble more and mor about how verbose it is. Honestly i would say i'm not sold on go for quick commandline tools. I see the great performance and simple deployment, but at the moment i wouldn't trade it for python, java or the powershell. But i will keep learning and maybe i will be convinced.