exec.Run – 这个Go程序有什么问题？

huangapple
go评论130阅读模式
英文:

exec.Run - What's wrong with this Go program?

问题

这个Golang程序不是应该将目录列表输出到标准输出吗？
它可以编译通过，但是没有任何输出。

  1. package main
  3. import "exec"
  5. func main() {
  6.   argv := []string{"-la"}
  7.   envv := []string{}
  8.   exec.Run("ls", argv, envv, "", exec.DevNull, exec.PassThrough, exec.MergeWithStdout)
  9. }
英文:

Isn't this Golang program supposed to output a directory listing to stdout?
It compiles ok, but does nothing.

  1. package main
  3. import "exec"
  5. func main() {
  6.   argv := []string{"-la"}
  7.   envv := []string{}
  8.   exec.Run("ls", argv, envv, "", exec.DevNull, exec.PassThrough, exec.MergeWithStdout)
  9. }

答案1

得分: 4

这段代码可以工作：

  1. package main
  2. import "exec"
  3.  
  4. func main() {
  5.   cmd, err := exec.Run("/bin/ls", []string{"/bin/ls", "-la"}, []string{}, "", exec.DevNull, exec.PassThrough, exec.PassThrough)
  6.   if (err != nil) {
  7.     return
  8.   }
  9.   cmd.Close()
  10. }
英文:

this works:

  1. package main
  2. import "exec"
  3.  
  4. func main() {
  5.   cmd, err := exec.Run("/bin/ls", []string{"/bin/ls", "-la"}, []string{}, "", exec.DevNull, exec.PassThrough, exec.PassThrough)
  6.   if (err != nil) {
  7.     return
  8.   }
  9.   cmd.Close()
  10. }

答案2

得分: 2

你也可以使用原生的Go语言来完成，使用ioutil.ReadDir(dir)，像这样：

  1. //listdir.go
  2. package main
  4. import (
  5. 	"os"
  6. 	"io/ioutil"
  7. 	"fmt"
  8. )
  10. func ListDir(dir string) ([]os.FileInfo, error) {
  11. 	return ioutil.ReadDir(dir)
  12. }
  14. func main() {
  15. 	dir := "./"
  16. 	if len(os.Args) > 1 {
  17. 		dir = os.Args[1]
  18. 	}
  19. 	fi, err := ListDir(dir)
  20. 	if err != nil {
  21. 		fmt.Println("错误", err)
  22. 	}
  24. 	for _, f := range fi {
  25. 		d := "-"
  26. 		if f.IsDir() { d = "d" }
  27. 		fmt.Printf("%s %o %d %s %s\n", d, f.Mode() & 0777, f.Size(), f.ModTime().Format("Jan 2 15:04"), f.Name())
  28. 	}
  29. }

请查看ioutil和os包的文档。

英文:

You could also do it in native go using: ioutil.ReadDir(dir), like so:

  1. //listdir.go
  2. package main
  4. import (
  5. 	"os"
  6. 	"io/ioutil"
  7. 	"fmt"
  8. )
  10. func ListDir(dir string) ([]os.FileInfo, error) {
  11. 	return ioutil.ReadDir(dir)
  12. }
  14. func main() {
  15. 	dir := "./"
  16. 	if len(os.Args) > 1 {
  17. 		dir = os.Args[1]
  18. 	}
  19. 	fi, err := ListDir(dir)
  20. 	if err != nil {
  21. 		fmt.Println("Error", err)
  22. 	}
  24. 	for _, f := range fi {
  25. 		d := "-"
  26. 		if f.IsDir() { d = "d" }
  27. 		fmt.Printf("%s %o %d %s %s\n", d, f.Mode() & 0777, f.Size(), f.ModTime().Format("Jan 2 15:04"), f.Name())
  28. 	}
  29. }

Checkout the documentation available for ioutil and os packages.

答案3

得分: 1

默认情况下，exec.Command会将标准输入、输出和错误连接到/dev/null。所以，你的'ls'命令运行得很好，但输出只是被丢弃了。如果你在exec.Run调用之前添加以下代码：

  1. cmd.Stdin = os.Stdin
  2. cmd.Stdout = os.Stdout
  3. cmd.Stderr = os.Stderr

那么你的输出将会被发送到你预期的位置。

英文:

By default exec.Command will leave standard input, output and error connected to /dev/null. So, your 'ls' command is running fine but the output is just being thrown away. If you add:

  1. cmd.Stdin = os.Stdin
  2. cmd.Stdout = os.Stdout
  3. cmd.Stderr = os.Stderr

before the exec.Run call then your output will go where you probably expect it.

答案4

得分: -1

exec.Run替换了您的程序，并执行它 -- 它永远不会返回到您的应用程序。这意味着当'cd'完成时，它将正常退出，唯一的影响应该是更改目录；'ls'将永远不会运行。

英文:

exec.Run replaces your program with the one it executes -- it never returns to your app. This means that when 'cd' completes, it will exit as normal, and the only effect should be of changing the directory; 'ls' will never run.

huangapple
  • 本文由 发表于 2010年9月14日 23:04:37
  • 转载请务必保留本文链接：https://go.coder-hub.com/3710167.html
  • go
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