lesson5/

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Homework-5

根据如下两个shell.go和pipe.go展示的内容完成一个支持管道的shell，例如：

ps aux | grep bash | grep -v grep 

shell.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"os/exec"
	"strings"
)

func main() {
	host, _ := os.Hostname()
	prompt := fmt.Sprintf("[icexin@%s]$ ", host)
	r := bufio.NewScanner(os.Stdin)
	//r := bufio.NewReader(os.Stdin)
	for {
		fmt.Print(prompt)
		if !r.Scan() {
			break
		}
		line := r.Text()
		// line, _ := r.ReadString('\n')
		// line = strings.TrimSpace(line)
		if len(line) == 0 {
			continue
		}
		var line_list []string
		var cmd_line, out_file string
		if strings.Contains(line, ">") {
			line_list = strings.Split(line, ">")
			cmd_line = line_list[0]
			out_file = strings.TrimSpace(line_list[1])
		} else {
			cmd_line = line
		}
		args := strings.Fields(cmd_line)
		// ls > a.txt
		//fmt.Println(args)
		cmd := exec.Command(args[0], args[1:]...)
		var out_fd *os.File
		if len(out_file) != 0 {
			out_fd, _ = os.OpenFile(out_file, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
			cmd.Stdout = out_fd
		} else {
			cmd.Stdout = os.Stdout
		}

		cmd.Stdin = os.Stdin
		cmd.Stderr = os.Stderr
		err := cmd.Run()
		if err != nil {
			fmt.Println(err)
		}
		if out_fd != nil {
			out_fd.Close()
		}
	}
}

pipe.go

package main

import (
	"io"
	"os"
	"os/exec"
	"strings"
)

func main() {
	line := "ls | grep file"
	cmds := strings.Split(line, "|")
	s1 := strings.Fields(cmds[0])
	s2 := strings.Fields(cmds[1])

	r, w := io.Pipe()
	cmd1 := exec.Command(s1[0], s1[1:]...)
	cmd2 := exec.Command(s2[0], s2[1:]...)
	cmd1.Stdin = os.Stdin
	cmd1.Stdout = w
	cmd2.Stdin = r
	cmd2.Stdout = os.Stdout
	cmd1.Start()
	cmd2.Start()

	cmd1.Wait()
	r.Close()
	w.Close()
	cmd2.Wait()
}