Golang – Write sentence to file

This recipe demonstrates how to use flag to build a command line program, how to convert string slice to string and how to write sentence to file specified by user.

Usage example: writefile -f test.txt hi this is a test.

package main

import (

func convertSliceToString(s []string) string {
	// Convert string slice to string
	return strings.Join(s, " ")

func writeFile(f, txt string) error {
	file, e := os.OpenFile(f, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if e != nil {
		return e
	defer file.Close()
	_, wrErr := io.WriteString(file, txt)
	if wrErr != nil {
		return wrErr
	return nil

func main() {
	filename := flag.String("f", "", "specify file name")
	// flag.Args() returns string slice.
	txt := convertSliceToString(flag.Args())
	e := writeFile(*filename, txt)
	if e != nil {


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