Source Code for Module rocon_utilities.system

  1  #!/usr/bin/env python 
  2  # 
  3  # License: BSD 
  4  #   https://raw.github.com/robotics-in-concert/rocon_multimaster/master/rocon_utilities/LICENSE 
  5  # 
  6   
  7  ############################################################################## 
  8  # Imports 
  9  ############################################################################## 
 10   
 11  import os 
 12  import time 
 13  import errno 
 14  # Local imports 
 15  from .exceptions import TimeoutExpiredError 
 16   
 17  ############################################################################## 
 18  # Methods 
 19  ############################################################################## 
 20   
 21   
 22 -def which(program): 
 23   
 24      def is_exe(fpath): 
 25          return os.path.isfile(fpath) and os.access(fpath, os.X_OK) 
 26   
 27      fpath, unused_fname = os.path.split(program) 
 28      if fpath: 
 29          if is_exe(program): 
 30              return program 
 31      else: 
 32          for path in os.environ["PATH"].split(os.pathsep): 
 33              path = path.strip('"') 
 34              exe_file = os.path.join(path, program) 
 35              if is_exe(exe_file): 
 36                  return exe_file 
 37   
 38      return None 
 39   
 40   
 41  ############################################################################## 
 42  # PID 
 43  ############################################################################## 
 44   
 45   
 46 -def pid_exists(pid): 
 47      """Check whether pid exists in the current process table.""" 
 48      if pid < 0: 
 49          return False 
 50      try: 
 51          os.kill(pid, 0) 
 52      except OSError, e: 
 53          return e.errno == errno.EPERM 
 54      else: 
 55          return True 
 56   
 57   
 58 -def wait_pid(pid, timeout=None): 
 59      """Wait for process with pid 'pid' to terminate and return its 
 60      exit status code as an integer. 
 61   
 62      If pid is not a children of os.getpid() (current process) just 
 63      waits until the process disappears and return None. 
 64   
 65      If pid does not exist at all return None immediately. 
 66   
 67      Raise TimeoutExpiredError on timeout expired (if specified). 
 68      """ 
 69      def check_timeout(delay): 
 70          if timeout is not None: 
 71              if time.time() >= stop_at: 
 72                  raise TimeoutExpiredError 
 73          time.sleep(delay) 
 74          return min(delay * 2, 0.04) 
 75   
 76      if timeout is not None: 
 77          waitcall = lambda: os.waitpid(pid, os.WNOHANG) 
 78          stop_at = time.time() + timeout 
 79      else: 
 80          waitcall = lambda: os.waitpid(pid, 0) 
 81   
 82      delay = 0.0001 
 83      while 1: 
 84          try: 
 85              retpid, status = waitcall() 
 86          except OSError, err: 
 87              if err.errno == errno.EINTR: 
 88                  delay = check_timeout(delay) 
 89                  continue 
 90              elif err.errno == errno.ECHILD: 
 91                  # This has two meanings: 
 92                  # - pid is not a child of os.getpid() in which case 
 93                  #   we keep polling until it's gone 
 94                  # - pid never existed in the first place 
 95                  # In both cases we'll eventually return None as we 
 96                  # can't determine its exit status code. 
 97                  while 1: 
 98                      if pid_exists(pid): 
 99                          delay = check_timeout(delay) 
100                      else: 
101                          return 
102              else: 
103                  raise 
104          else: 
105              if retpid == 0: 
106                  # WNOHANG was used, pid is still running 
107                  delay = check_timeout(delay) 
108                  continue 
109              # process exited due to a signal; return the integer of 
110              # that signal 
111              if os.WIFSIGNALED(status): 
112                  return os.WTERMSIG(status) 
113              # process exited using exit(2) system call; return the 
114              # integer exit(2) system call has been called with 
115              elif os.WIFEXITED(status): 
116                  return os.WEXITSTATUS(status) 
117              else: 
118                  # should never happen 
119                  raise RuntimeError("unknown process exit status") 
120