Go - Getting Started with Go and Unix Systems Programming - Hello, World!

Go Systems Programming:
Master Linux and Unix
system level programming with Go
楽天ブックス 紀伊國屋書店

開発環境

• macOS Catalina - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Go (プログラミング言語)

Go Systems Programming: Master Linux and Unix system level programming with Go (Mihalis Tsoukalos(著)、Packt Publishing)のChapter 1(Getting Started with Go and Unix Systems Programming)、Exercisesの解答を求めてみる。

コード

package main

import (
 "fmt"
 "io/ioutil"
 "os"
)

func main() {
 fmt.Println("3.")
 fmt.Println("Hello, World!")

 fmt.Println("7.")
 if len(os.Args) < 2 {
  fmt.Fprintln(os.Stderr, "Usage: sample1 <filename>")
  os.Exit(1)
 }
 input, err := ioutil.ReadFile(os.Args[1])
 if err != nil {
  fmt.Fprintln(os.Stderr, err)
  os.Exit(1)
 }
 fmt.Println(string(input))
}

入出力結果(Zsh、PowerShell、Terminal)

% go build sample1.go
% ./sample1          
3.
Hello, World!
7.
Usage: sample1 <filename>
% ./sample1 a
3.
Hello, World!
7.
open a: no such file or directory
% ./sample1 sample1.go
3.
Hello, World!
7.
package main

import (
 "fmt"
 "io/ioutil"
 "os"
)

func main() {
 fmt.Println("3.")
 fmt.Println("Hello, World!")

 fmt.Println("7.")
 if len(os.Args) < 2 {
  fmt.Fprintln(os.Stderr, "Usage: sample1 <filename>")
  os.Exit(1)
 }
 input, err := ioutil.ReadFile(os.Args[1])
 if err != nil {
  fmt.Fprintln(os.Stderr, err)
  os.Exit(1)
 }
 fmt.Println(string(input))
}

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