英文:
How to read from Go additional file descriptors when running a command
问题
假设我有一个程序，它在文件描述符3上输出内容，就像这样：
package main
import "os"
func main() {
fd3 := os.NewFile(3, "fd3")
fd3.Write([]byte("FOOBAR\n"))
fd3.Close()
}
现在，我想从一个Go程序中获取发送到文件描述符3的输出：
package main
import (
"bufio"
"fmt"
"os/exec"
"os"
)
func main() {
cmd := exec.Command("./client")
cmd.Stderr = os.Stderr
fd3 := os.NewFile(3, "fd3")
defer fd3.Close()
cmd.ExtraFiles = []*os.File{fd3}
err := cmd.Start()
if err != nil {
panic(err)
}
go func() {
for {
reader := bufio.NewReader(fd3)
line, err := reader.ReadString('\n')
if err != nil {
panic(err)
}
fmt.Print(line)
}
}()
cmd.Wait()
fmt.Println("--- END ---")
}
但是，这段代码不起作用，它输出以下错误：
panic: read fd3: bad file descriptor
我不明白我的代码有什么问题。有人愿意帮忙吗？
英文:
Let's say I have a program than outputs things on file descriptor 3; something like this:
package main
import "os"
func main() {
fd3 := os.NewFile(3, "fd3")
fd3.Write([]byte("FOOBAR\n"))
fd3.Close()
}
Now, I want to get the output sent to file descriptor 3 from a Go program:
package main
import (
"bufio"
"fmt"
"os/exec"
"os"
)
func main() {
cmd := exec.Command("./client")
cmd.Stderr = os.Stderr
fd3 := os.NewFile(3, "fd3")
defer fd3.Close()
cmd.ExtraFiles = []*os.File{fd3}
err := cmd.Start()
if err != nil {
panic(err)
}
go func() {
for {
reader := bufio.NewReader(fd3)
line, err := reader.ReadString('\n')
if err != nil {
panic(err)
}
fmt.Print(line)
}
}()
cmd.Wait()
fmt.Println("--- END ---")
}
But that does not work as it outputs the following error:
panic: read fd3: bad file descriptor
I don't understand what's wrong with my code. Anyone willing to help?
答案1
得分: 3
os.NewFile实际上并不打开文件描述符。它实际上是一个API，用于包装给定给你的文件描述符。
请查看godoc：http://golang.org/pkg/os/#Create
（点击名称Create，它当前指向this）
我认为你想调用os.Create(name)并将文件描述符传递给子进程，或者可能需要使用os.Open / os.OpenFile来设置模式等。
英文:
os.NewFile doesn't actually open a file descriptor. It's really an API to wrap a fd that was given to you.
look at the godoc: http://golang.org/pkg/os/#Create
(click the name Create, which currently points to this)
I think you want to call os.Create(name) and pass the fd to the child process
or potentiall os.Open / os.OpenFile if you need to set mode and stuff
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