Golang: how can filename arguments be parsed?

I am writing a command line utility in golang, which takes a file as an argument. How can I accurately turn this argument into a useable file? It seems there are many cases to handle:

• An absolute path has been given, and I should use it as is
• A relative path has been given, and I should path.Join() it with the current working directory
• "."'s and "../"'s are used in the path, and I believe I should still use path.Join() and Go will simplify the path?

Does Go provide anything to handle this? Should I just branch based on whether the first character is '/'? That seems like a hacky solution, but perhaps it always works and so should be done?

The operating system interprets paths for you. You don't need to do anything with path names. You can simply do something like this:

os.Open("./path/to/file")
os.Open("another/file")
os.Open("../some_file")

et cetera

Taking aside that you don't want to see . as a file, there's not that much to worry about.

In a trusted environment*, where the user can indeed point to <i>any</i> file, the os package will take care of it. No need to filepath.Join anything.

• If an absolute path is given, it will open it. (i.e.: starting with /)
• If not, then it will see it relative to the current working directory. (including . and ./)

(*) In a non-trusted environment (a web server for example), you will want to validate the path given for authorization.

OS does hard work for you. However passed argument possible can correspond a directory. You should either check os.FileInfo.IsDir, or implement path.filepath.WalkFunc() taken by path.filepath.Walk() for batch operations. Latter is quite a common approach.