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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2018 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package osutil
import (
"context"
"io"
"os/exec"
"sync"
"sync/atomic"
"syscall"
)
// ContextWriter returns a discarding io.Writer which Write method
// returns an error once the context is done.
func ContextWriter(ctx context.Context) io.Writer {
return ctxWriter{ctx}
}
type ctxWriter struct {
ctx context.Context
}
func (w ctxWriter) Write(p []byte) (n int, err error) {
select {
case <-w.ctx.Done():
return 0, w.ctx.Err()
default:
}
return len(p), nil
}
// RunWithContext runs the given command, but kills it if the context
// becomes done before the command finishes.
func RunWithContext(ctx context.Context, cmd *exec.Cmd) error {
if err := ctx.Err(); err != nil {
return err
}
if err := cmd.Start(); err != nil {
return err
}
var ctxDone uint32
var wg sync.WaitGroup
waitDone := make(chan struct{})
wg.Add(1)
go func() {
select {
case <-ctx.Done():
atomic.StoreUint32(&ctxDone, 1)
cmd.Process.Kill()
case <-waitDone:
}
wg.Done()
}()
err := cmd.Wait()
close(waitDone)
wg.Wait()
if atomic.LoadUint32(&ctxDone) != 0 {
// do one last check to make sure the error from Wait is what we expect from Kill
if err, ok := err.(*exec.ExitError); ok {
if ws, ok := err.ProcessState.Sys().(syscall.WaitStatus); ok && ws.Signal() == syscall.SIGKILL {
return ctx.Err()
}
}
}
return err
}
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