How to Idiomatically Read Lines from a File in Go?

Idiomatic Line Reading in Go

Despite the availability of low-level byte array-returning line reading functions in Go's standard library, an easier and more idiomatic approach exists for obtaining strings from a readline operation.

Solution

To seamlessly read line-by-line from a file, the Readln(*bufio.Reader) function can be employed. It retrieves a line (excluding the linefeed character) from the provided bufio.Reader struct.

Here's a code snippet demonstrating the usage of Readln:

// Readln returns a single line (without the ending \n)
// from the input buffered reader.
// An error is returned iff there is an error with the
// buffered reader.
func Readln(r *bufio.Reader) (string, error) {
  var (isPrefix bool = true
       err error = nil
       line, ln []byte
      )
  for isPrefix && err == nil {
      line, isPrefix, err = r.ReadLine()
      ln = append(ln, line...)
  }
  return string(ln),err
}

This function can be utilized to read each line from a file:

f, err := os.Open(fi)
if err != nil {
    fmt.Println("error opening file= ",err)
    os.Exit(1)
}
r := bufio.NewReader(f)
s, e := Readln(r)
for e == nil {
    fmt.Println(s)
    s,e = Readln(r)
}

This code reads line by line from the specified file and prints each line to standard output.

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