Returning File Pointer in Golang

Question

I'm still struggling with the basics of Golang.

Consider the following sample code:

func OpenOutputFile(name string) (fp *os.File) {
  fp, err := os.Create(name)
  if err != nil {
      panic(err)
  }

  defer func() {
      if err := fp.Close(); err != nil {
          panic(err)
      }
  }()

  return fp
}

I would assume that calling:

fp := OpenOutputFile("output.txt")

would now make fp a file pointer (*os.File), so that I could call a statement like:

io.WriteString(fp, "Hello World")

In another function. But when calling this method, the error is generated:

0 write output.txt: bad file descriptor

So it appears that the pointer returned is not valid. How can I return a properly formed pointer to use with io.WriteString?

I appreciate the help!

Of note: Everything executes as intended when the creation of the file pointer and the writing to the file pointer exists in the same method. Breaking the logic into a function causes it to not behave as intended.

Returning File Pointer in Golang

1 Answers