How Can I Efficiently Read a Line into a String in Go?

Efficiently Reading a Line to String in Go

The Go standard library provides low-level functions for reading input, returning byte arrays instead of strings. For ease of use, we explore an alternative approach to obtaining a string directly from a readline function.

Custom Readln Function

To simplify readline operations, we create a custom Readln function that reads a single line (excluding the newline character) from a provided bufio.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
}

Example Usage

Using the Readln function, we can read lines from a file and print them to stdout:

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 approach avoids the need to manually convert byte arrays to strings, streamlining the process of obtaining strings from readline functions in Go.

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