douyongdao4046
2016-09-15 09:53
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golang exec后台进程并获取其pid

Situation:

I want to run a command that puts itself into the background. If it makes it more possible, then I'll run the command in foreground and bring it into the background by myself.

Question:

When the process runs in background: how can I get it's pid using Go?

I tried the following:

cmd := exec.Command("ssh", "-i", keyFile, "-o", "ExitOnForwardFailure yes", "-fqnNTL", fmt.Sprintf("%d:127.0.0.1:%d", port, port), fmt.Sprintf("%s@%s", serverUser, serverIP))
cmd.Start()
pid := cmd.Process.Pid
cmd.Wait()

This returns instantly and leaves ssh running in the background. But it's pid is not the pid of the running ssh process. Moreover, it's the pid of the parent ssh process before it forked and backgrounded itself.

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2条回答 默认 最新

  • douhao7677 2016-09-15 14:02
    已采纳

    You don't need anything special, just don't tell ssh to background itself and don't Wait() for it. Example:

    $ cat script.sh
    #!/bin/sh
    sleep 1
    echo "I'm the script with pid $$"
    for i in 1 2 3; do
            sleep 1
            echo "Still running $$"
    done
    $ cat proc.go
    package main
    
    import (
           "log"
           "os"
           "os/exec"
    )
    
    func main() {
         cmd := exec.Command("./script.sh")
         cmd.Stdout = os.Stdout
         err := cmd.Start()
         if err != nil {
            log.Fatal(err)
         }
         log.Printf("Just ran subprocess %d, exiting
    ", cmd.Process.Pid)
    }
    $ go run proc.go
    2016/09/15 17:01:03 Just ran subprocess 3794, exiting
    $ I'm the script with pid 3794
    Still running 3794
    Still running 3794
    Still running 3794
    
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  • dqwh1203 2018-10-11 19:38

    @Mostafa Hussein, can use goroutine waiting, manage process

    function main()
        cmd := exec.Command( "shell.sh" )
        err := cmd.Start()
        if err != nil {
            return err
        }
        pid := cmd.Process.Pid
        // use goroutine waiting, manage process
        // this is important, otherwise the process becomes in S mode
        go func() { 
            err = cmd.Wait()
            fmt.Printf("Command finished with error: %v", err)
        }()
        return nil
    }
    
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