How to Efficiently Read a Line from a File as a String in Go?

readline to String in Go

In Go, the standard library provides low-level raw functions for readline operations, which return byte arrays. Is there a more convenient method to obtain a string from a readline function?

Idiomatic Solution

The idiomatic approach to readline to string in Go is to utilize the bufio.Reader struct. The Readln() function returns a line (without the trailing newline n) from the input buffered reader.

import (
    "bufio"
    "fmt"
    "os"
)

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
}

func main() {
    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 function reads lines from a file, stripping the newline character (n) and printing each line to the console.

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