pgrp.go

package main

import (
        "log"
        "os"
        "os/signal"
        "syscall"

        "github.com/elves/elvish/sys"
)

func main() {
        signal.Ignore(syscall.SIGTTOU)

        sysattr := syscall.SysProcAttr{Setpgid: true}
        attr := syscall.ProcAttr{Env: os.Environ(), Files: []uintptr{0, 1, 2}, Sys: &sysattr}
        path := "/bin/sleep"
        args := []string{path, "5"}
        pid, err := syscall.ForkExec(path, args, &attr)
        if err != nil {
                log.Fatal(err)
        }
        log.Println("spawned sleep, pid", pid)

        err = sys.Tcsetpgrp(0, pid)
        if err != nil {
                log.Fatal(err)
        }
        log.Println("put sleep in fg")

        var ws syscall.WaitStatus
        _, err = syscall.Wait4(pid, &ws, syscall.WUNTRACED, nil)
        if err != nil {
                log.Fatal(err)
        }
        log.Println("sleep terminated with", ws)

        err = sys.Tcsetpgrp(0, syscall.Getpgrp())
        if err != nil {
                log.Fatal(err)
        }
        log.Println("put my own pgrp back in fg")
}