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239 lines
7.5 KiB
Go
239 lines
7.5 KiB
Go
// -*- Mode: Go; indent-tabs-mode: t -*-
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/*
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* Copyright (C) 2017 Canonical Ltd
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 3 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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package osutil_test
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import (
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"bytes"
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"fmt"
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"os"
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"os/exec"
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"path/filepath"
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"time"
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. "gopkg.in/check.v1"
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"github.com/snapcore/snapd/osutil"
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)
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type flockSuite struct{}
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var _ = Suite(&flockSuite{})
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// Test that an existing lock file can be opened.
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func (s *flockSuite) TestOpenExistingLockForReading(c *C) {
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fname := filepath.Join(c.MkDir(), "name")
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lock, err := osutil.OpenExistingLockForReading(fname)
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c.Assert(err, ErrorMatches, ".* no such file or directory")
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c.Assert(lock, IsNil)
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lock, err = osutil.NewFileLockWithMode(fname, 0644)
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c.Assert(err, IsNil)
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lock.Close()
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// Having created the lock above, we can now open it correctly.
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lock, err = osutil.OpenExistingLockForReading(fname)
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c.Assert(err, IsNil)
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defer lock.Close()
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// The lock file is read-only though.
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file := lock.File()
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defer file.Close()
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n, err := file.Write([]byte{1, 2, 3})
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// write(2) returns EBADF if the file descriptor is read only.
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c.Assert(err, ErrorMatches, ".* bad file descriptor")
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c.Assert(n, Equals, 0)
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}
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// Test that opening and closing a lock works as expected, and that the mode is right.
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func (s *flockSuite) TestNewFileLockWithMode(c *C) {
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lock, err := osutil.NewFileLockWithMode(filepath.Join(c.MkDir(), "name"), 0644)
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c.Assert(err, IsNil)
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defer lock.Close()
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fi, err := os.Stat(lock.Path())
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c.Assert(err, IsNil)
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c.Assert(fi.Mode().Perm(), Equals, os.FileMode(0644))
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}
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// Test that opening and closing a lock works as expected.
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func (s *flockSuite) TestNewFileLock(c *C) {
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lock, err := osutil.NewFileLock(filepath.Join(c.MkDir(), "name"))
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c.Assert(err, IsNil)
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defer lock.Close()
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fi, err := os.Stat(lock.Path())
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c.Assert(err, IsNil)
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c.Assert(fi.Mode().Perm(), Equals, os.FileMode(0600))
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}
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// Test that we can access the underlying open file.
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func (s *flockSuite) TestFile(c *C) {
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fname := filepath.Join(c.MkDir(), "name")
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lock, err := osutil.NewFileLock(fname)
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c.Assert(err, IsNil)
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defer lock.Close()
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f := lock.File()
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c.Assert(f, NotNil)
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c.Check(f.Name(), Equals, fname)
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}
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func flockSupportsConflictExitCodeSwitch(c *C) bool {
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output, err := exec.Command("flock", "--help").CombinedOutput()
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c.Assert(err, IsNil)
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return bytes.Contains(output, []byte("--conflict-exit-code"))
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}
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// Test that Lock and Unlock work as expected.
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func (s *flockSuite) TestLockUnlockWorks(c *C) {
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if !flockSupportsConflictExitCodeSwitch(c) {
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c.Skip("flock too old for this test")
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}
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lock, err := osutil.NewFileLock(filepath.Join(c.MkDir(), "name"))
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c.Assert(err, IsNil)
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defer lock.Close()
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// Run a flock command in another process, it should succeed because it can
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// lock the lock as we didn't do it yet.
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cmd := exec.Command("flock", "--exclusive", "--nonblock", lock.Path(), "true")
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c.Assert(cmd.Run(), IsNil)
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// Lock the lock.
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c.Assert(lock.Lock(), IsNil)
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// Run a flock command in another process, it should fail with the distinct
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// error code because we hold the lock already and we asked it not to block.
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cmd = exec.Command("flock", "--exclusive", "--nonblock",
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"--conflict-exit-code", "2", lock.Path(), "true")
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c.Assert(cmd.Run(), ErrorMatches, "exit status 2")
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// Unlock the lock.
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c.Assert(lock.Unlock(), IsNil)
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// Run a flock command in another process, it should succeed because it can
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// grab the lock again now.
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cmd = exec.Command("flock", "--exclusive", "--nonblock", lock.Path(), "true")
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c.Assert(cmd.Run(), IsNil)
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}
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// Test that ReadLock and Unlock work as expected.
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func (s *flockSuite) TestReadLockUnlockWorks(c *C) {
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if !flockSupportsConflictExitCodeSwitch(c) {
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c.Skip("flock too old for this test")
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}
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lock, err := osutil.NewFileLock(filepath.Join(c.MkDir(), "name"))
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c.Assert(err, IsNil)
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defer lock.Close()
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// Run a flock command in another process, it should succeed because it can
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// lock the lock as we didn't do it yet.
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cmd := exec.Command("flock", "--exclusive", "--nonblock", lock.Path(), "true")
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c.Assert(cmd.Run(), IsNil)
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// Grab a shared lock.
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c.Assert(lock.ReadLock(), IsNil)
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// Run a flock command in another process, it should fail with the distinct
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// error code because we hold a shared lock already and we asked it not to block.
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cmd = exec.Command("flock", "--exclusive", "--nonblock",
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"--conflict-exit-code", "2", lock.Path(), "true")
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c.Assert(cmd.Run(), ErrorMatches, "exit status 2")
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// Run a flock command in another process, it should succeed because we
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// hold a shared lock and those do not prevent others from acquiring a
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// shared lock.
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cmd = exec.Command("flock", "--shared", "--nonblock",
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"--conflict-exit-code", "2", lock.Path(), "true")
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c.Assert(cmd.Run(), IsNil)
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// Unlock the lock.
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c.Assert(lock.Unlock(), IsNil)
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// Run a flock command in another process, it should succeed because it can
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// grab the lock again now.
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cmd = exec.Command("flock", "--exclusive", "--nonblock", lock.Path(), "true")
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c.Assert(cmd.Run(), IsNil)
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}
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// Test that locking a locked lock does nothing.
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func (s *flockSuite) TestLockLocked(c *C) {
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lock, err := osutil.NewFileLock(filepath.Join(c.MkDir(), "name"))
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c.Assert(err, IsNil)
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defer lock.Close()
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// NOTE: technically this replaces the lock type but we only use LOCK_EX.
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c.Assert(lock.Lock(), IsNil)
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c.Assert(lock.Lock(), IsNil)
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}
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// Test that unlocking an unlocked lock does nothing.
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func (s *flockSuite) TestUnlockUnlocked(c *C) {
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lock, err := osutil.NewFileLock(filepath.Join(c.MkDir(), "name"))
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c.Assert(err, IsNil)
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defer lock.Close()
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c.Assert(lock.Unlock(), IsNil)
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}
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// Test that locking or unlocking a closed lock fails.
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func (s *flockSuite) TestUsingClosedLock(c *C) {
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lock, err := osutil.NewFileLock(filepath.Join(c.MkDir(), "name"))
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c.Assert(err, IsNil)
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lock.Close()
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c.Assert(lock.Lock(), ErrorMatches, "bad file descriptor")
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c.Assert(lock.Unlock(), ErrorMatches, "bad file descriptor")
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}
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// Test that non-blocking locking reports error on pre-acquired lock.
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func (s *flockSuite) TestLockUnlockNonblockingWorks(c *C) {
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// Use the "flock" command to grab a lock for 9999 seconds in another process.
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lockPath := filepath.Join(c.MkDir(), "lock")
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sleeperKillerPath := filepath.Join(c.MkDir(), "pid")
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// we can't use --no-fork because we still support 14.04
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cmd := exec.Command("flock", "--exclusive", lockPath, "-c", fmt.Sprintf(`echo "kill $$" > %s && exec sleep 30`, sleeperKillerPath))
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// flock uses the env variable 'SHELL' to run the passed in command. a non-posix
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// shell will not understand $$. we can force flock to use its default by unsetting
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// the variable
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cmd.Env = append(cmd.Env, "SHELL=")
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c.Assert(cmd.Start(), IsNil)
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defer func() { exec.Command("/bin/sh", sleeperKillerPath).Run() }()
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// Give flock some chance to create the lock file.
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for i := 0; i < 10; i++ {
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if osutil.FileExists(lockPath) {
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break
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}
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time.Sleep(time.Millisecond * 300)
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}
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// Try to acquire the same lock file and see that it is busy.
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lock, err := osutil.NewFileLock(lockPath)
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c.Assert(err, IsNil)
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c.Assert(lock, NotNil)
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defer lock.Close()
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c.Assert(lock.TryLock(), Equals, osutil.ErrAlreadyLocked)
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}
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