Get file size

https://codeeval.dev/gist/ef21b4629b5650feda628b673e0cb5e5

Instead of os.Stat we can also use os.Lstat. The difference is that os.Stat follows symbolic links and os.Lstat doesn’t.

In other words: for a symbolic link os.Lstat returns information about link and os.Stat about the file that it links to.

Get information about the file

https://codeeval.dev/gist/f3200e74ea0cb6cb456b2c973c7bd9ce

Check if a file exists

https://codeeval.dev/gist/076b9dc06c9fa4db02a52c8c3ec828e8

Checking if a file exists is surprisingly tricky and it’s impossible to write a generic function that handles all the nuances.

Here are decisions we made:

• it treats files and directories the same. If a path exists and you want to distinguish between directory and a file, you would need to call IsDir() on result of os.Lstat
• if a file is a symbolic link, do we test the link or the real file it links to? We used os.Lstat so we test the link. We could also use os.Stat to resolve the symbolic link
• “path doesn’t exist” is only one of possible errors returned by os.Lstat. Do we want to distinguish between “file doesn’t exist” and “file exists and we don’t have access”? We decided to be more informative but in some cases it would be simpler to just return a bool and always return false if os.Lstat fails

Delete a file

path := "foo.txt"
err := os.Remove(path)
if err != nil {
    if os.IsNotExist(err) {
        fmt.Printf("os.Remove failed because file doesn't exist\\n")
    } else {
        fmt.Printf("os.Remove failed with '%s'\\n", err)
    }
}

os.Remove returns an error for files that don’t exist.

Usually you want to ignore such errors which you can do by testing error with os.IsNotExist(err).

Rename a file

oldPath := "old_name.txt"
newPath := "new_name.txt"
err := os.Rename(oldPath, newPath)
if err != nil {
    fmt.Printf("os.Rename failed with '%s'\\n", err)
}

Copy a file