os.Wait on more than 1 process
creack
I am using ForkExec in loop and I would like to wait for all them
after the loop. In C, this would be with WAIT_ANY, but I didn't
managed to get it in Go.
I tried os.Wait() with -1/0 as pid but it didn't really understand
what was the result, I had a lot of notifications but none for my
childs processes.
I tried with cgo to call waitpid() but it does not see child process.
I could use os.Wait() with a specific pid and launch it in goroutines,
but it seems very complicated for what it is.
Someone have an idea?
Marcin 'Qrczak' Kowalczyk
> I could use os.Wait() with a specific pid and launch it in goroutines,
> but it seems very complicated for what it is.
I don't understand the problem. Just wait for all pids you launched
sequentially.
--
Marcin Kowalczyk
Gustavo Niemeyer
> I tried os.Wait() with -1/0 as pid but it didn't really understand
> what was the result, I had a lot of notifications but none for my
> childs processes.
I don't know what you're doing there, but this works fine here:
package main
import "os"
func sleep() {
os.ForkExec("/bin/sh", []string{"/bin/sh", "-c", "sleep 3"},
[]string{}, "", nil)
}
func main() {
sleep()
sleep()
for i := 0; i != 2; i++ {
msg, _ := os.Wait(-1, 0)
println(msg.Pid, " exited")
}
}
--
Gustavo Niemeyer
http://niemeyer.net
http://niemeyer.net/blog
http://niemeyer.net/twitter
creack
And with this option, this code does not work.
@Marcin: I can't wait sequentially, I need to launch all processes and
then to wait for them. Any of them could end first and I need to
report it.
Gustavo Niemeyer
> And with this option, this code does not work.
Using os.Wait(-1, os.WUNTRACED) in the provided snippet works fine for
me as well.
creack
package main
import "os"
func sleep() {
os.ForkExec("/bin/sh", []string{"/bin/sh", "-c", "sleep 3"},
[]string{}, "", nil)
}
func main() {
sleep()
sleep()
for i := 0; i != 2; i++ {
msg, _ := os.Wait(-1,
println(msg.Pid, " exited")
}
}
$>6g test.go && 6l test.6 && ./6.out
0 exited
0 exited
Gustavo Niemeyer
With Ubuntu 10.10 on amd64 it works fine:
22442 exited
22444 exited
Would be worth debugging further to see where the issue is.
Benny Siegert
On Tue, 28 Dec 2010, creack wrote:
> I am using ForkExec in loop and I would like to wait for all them
> after the loop. In C, this would be with WAIT_ANY, but I didn't
> managed to get it in Go.
I was told that using wait with PID 0 or -1 is dangerous in Go, due to
the way the runtime works. Using one goroutine per fork is the easiest
way:
import (
"fmt"
"os"
)
func doSomething(arg string, status chan *os.Waitmsg) {
pid, err := os.ForkExec( ... )
if err != nil { ... }
w, err := os.Wait(pid, 0)
// ... check value of err
status <- w
}
func main() {
var num int
status := make(chan *os.Waitmsg)
for _, arg := range os.Args[1:] {
go doSomething(arg, status)
num++
}
for i := 0; i < num; i++ {
w := <-status
if w != nil && w.Exited() {
fmt.Printf("Child (pid %v) exited with status
%v\n", w.Pid, w.ExitStatus())
}
}
}
--Benny.
creack
the issue tracker.
On linux, it works fine. Thank you.
David Roundy
possibly a chan), provided there aren't incredibly many incredibly
tiny processes being spawned.
David
--
David Roundy