text: #!/usr/bin/env python
  
  # Copyright (c) 2009, Giampaolo Rodola'. All rights reserved.
  # Use of this source code is governed by a BSD-style license that can be
  # found in the LICENSE file.
  
  """Linux platform implementation."""
  
  from __future__ import division
  
  import base64
  import errno
  import functools
  import os
  import re
  import socket
  import struct
  import sys
  import warnings
  from collections import namedtuple, defaultdict
  
  from psutil import _common
  from psutil import _psposix
  from psutil._common import (isfile_strict, usage_percent, deprecated)
  from psutil._compat import PY3
  import _psutil_linux as cext
  import _psutil_posix
  
  
  __extra__all__ = [
      # io prio constants
      "IOPRIO_CLASS_NONE", "IOPRIO_CLASS_RT", "IOPRIO_CLASS_BE",
      "IOPRIO_CLASS_IDLE",
      # connection status constants
      "CONN_ESTABLISHED", "CONN_SYN_SENT", "CONN_SYN_RECV", "CONN_FIN_WAIT1",
      "CONN_FIN_WAIT2", "CONN_TIME_WAIT", "CONN_CLOSE", "CONN_CLOSE_WAIT",
      "CONN_LAST_ACK", "CONN_LISTEN", "CONN_CLOSING",
      # other
      "phymem_buffers", "cached_phymem"]
  
  
  # --- constants
  
  HAS_PRLIMIT = hasattr(cext, "linux_prlimit")
  
  # RLIMIT_* constants, not guaranteed to be present on all kernels
  if HAS_PRLIMIT:
      for name in dir(cext):
          if name.startswith('RLIM'):
              __extra__all__.append(name)
  
  # Number of clock ticks per second
  CLOCK_TICKS = os.sysconf("SC_CLK_TCK")
  PAGESIZE = os.sysconf("SC_PAGE_SIZE")
  BOOT_TIME = None  # set later
  DEFAULT_ENCODING = sys.getdefaultencoding()
  
  # ioprio_* constants http://linux.die.net/man/2/ioprio_get
  IOPRIO_CLASS_NONE = 0
  IOPRIO_CLASS_RT = 1
  IOPRIO_CLASS_BE = 2
  IOPRIO_CLASS_IDLE = 3
  
  # taken from /fs/proc/array.c
  PROC_STATUSES = {
      "R": _common.STATUS_RUNNING,
      "S": _common.STATUS_SLEEPING,
      "D": _common.STATUS_DISK_SLEEP,
      "T": _common.STATUS_STOPPED,
      "t": _common.STATUS_TRACING_STOP,
      "Z": _common.STATUS_ZOMBIE,
      "X": _common.STATUS_DEAD,
      "x": _common.STATUS_DEAD,
      "K": _common.STATUS_WAKE_KILL,
      "W": _common.STATUS_WAKING
  }
  
  # http://students.mimuw.edu.pl/lxr/source/include/net/tcp_states.h
  TCP_STATUSES = {
      "01": _common.CONN_ESTABLISHED,
      "02": _common.CONN_SYN_SENT,
      "03": _common.CONN_SYN_RECV,
      "04": _common.CONN_FIN_WAIT1,
      "05": _common.CONN_FIN_WAIT2,
      "06": _common.CONN_TIME_WAIT,
      "07": _common.CONN_CLOSE,
      "08": _common.CONN_CLOSE_WAIT,
      "09": _common.CONN_LAST_ACK,
      "0A": _common.CONN_LISTEN,
      "0B": _common.CONN_CLOSING
  }
  
  # set later from __init__.py
  NoSuchProcess = None
  AccessDenied = None
  TimeoutExpired = None
  
  
  # --- named tuples
  
  def _get_cputimes_fields():
      """Return a namedtuple of variable fields depending on the
      CPU times available on this Linux kernel version which may be:
      (user, nice, system, idle, iowait, irq, softirq, [steal, [guest,
       [guest_nice]]])
      """
      with open('/proc/stat', 'rb') as f:
          values = f.readline().split()[1:]
      fields = ['user', 'nice', 'system', 'idle', 'iowait', 'irq', 'softirq']
      vlen = len(values)
      if vlen >= 8:
          # Linux >= 2.6.11
          fields.append('steal')
      if vlen >= 9:
          # Linux >= 2.6.24
          fields.append('guest')
      if vlen >= 10:
          # Linux >= 3.2.0
          fields.append('guest_nice')
      return fields
  
  
  scputimes = namedtuple('scputimes', _get_cputimes_fields())
  
  svmem = namedtuple(
      'svmem', ['total', 'available', 'percent', 'used', 'free',
                'active', 'inactive', 'buffers', 'cached'])
  
  pextmem = namedtuple('pextmem', 'rss vms shared text lib data dirty')
  
  pmmap_grouped = namedtuple(
      'pmmap_grouped', ['path', 'rss', 'size', 'pss', 'shared_clean',
                        'shared_dirty', 'private_clean', 'private_dirty',
                        'referenced', 'anonymous', 'swap'])
  
  pmmap_ext = namedtuple(
      'pmmap_ext', 'addr perms ' + ' '.join(pmmap_grouped._fields))
  
  
  # --- system memory
  
  def virtual_memory():
      total, free, buffers, shared, _, _ = cext.linux_sysinfo()
      cached = active = inactive = None
      with open('/proc/meminfo', 'rb') as f:
          for line in f:
              if line.startswith(b"Cached:"):
                  cached = int(line.split()[1]) * 1024
              elif line.startswith(b"Active:"):
                  active = int(line.split()[1]) * 1024
              elif line.startswith(b"Inactive:"):
                  inactive = int(line.split()[1]) * 1024
              if (cached is not None
                      and active is not None
                      and inactive is not None):
                  break
          else:
              # we might get here when dealing with exotic Linux flavors, see:
              # https://github.com/giampaolo/psutil/issues/313
              msg = "'cached', 'active' and 'inactive' memory stats couldn't " \
                    "be determined and were set to 0"
              warnings.warn(msg, RuntimeWarning)
              cached = active = inactive = 0
      avail = free + buffers + cached
      used = total - free
      percent = usage_percent((total - avail), total, _round=1)
      return svmem(total, avail, percent, used, free,
                   active, inactive, buffers, cached)
  
  
  def swap_memory():
      _, _, _, _, total, free = cext.linux_sysinfo()
      used = total - free
      percent = usage_percent(used, total, _round=1)
      # get pgin/pgouts
      with open("/proc/vmstat", "rb") as f:
          sin = sout = None
          for line in f:
              # values are expressed in 4 kilo bytes, we want bytes instead
              if line.startswith(b'pswpin'):
                  sin = int(line.split(b' ')[1]) * 4 * 1024
              elif line.startswith(b'pswpout'):
                  sout = int(line.split(b' ')[1]) * 4 * 1024
              if sin is not None and sout is not None:
                  break
          else:
              # we might get here when dealing with exotic Linux flavors, see:
              # https://github.com/giampaolo/psutil/issues/313
              msg = "'sin' and 'sout' swap memory stats couldn't " \
                    "be determined and were set to 0"
              warnings.warn(msg, RuntimeWarning)
              sin = sout = 0
      return _common.sswap(total, used, free, percent, sin, sout)
  
  
  @deprecated(replacement='psutil.virtual_memory().cached')
  def cached_phymem():
      return virtual_memory().cached
  
  
  @deprecated(replacement='psutil.virtual_memory().buffers')
  def phymem_buffers():
      return virtual_memory().buffers
  
  
  # --- CPUs
  
  def cpu_times():
      """Return a named tuple representing the following system-wide
      CPU times:
      (user, nice, system, idle, iowait, irq, softirq [steal, [guest,
       [guest_nice]]])
      Last 3 fields may not be available on all Linux kernel versions.
      """
      with open('/proc/stat', 'rb') as f:
          values = f.readline().split()
      fields = values[1:len(scputimes._fields) + 1]
      fields = [float(x) / CLOCK_TICKS for x in fields]
      return scputimes(*fields)
  
  
  def per_cpu_times():
      """Return a list of namedtuple representing the CPU times
      for every CPU available on the system.
      """
      cpus = []
      with open('/proc/stat', 'rb') as f:
          # get rid of the first line which refers to system wide CPU stats
          f.readline()
          for line in f:
              if line.startswith(b'cpu'):
                  values = line.split()
                  fields = values[1:len(scputimes._fields) + 1]
                  fields = [float(x) / CLOCK_TICKS for x in fields]
                  entry = scputimes(*fields)
                  cpus.append(entry)
          return cpus
  
  
  def cpu_count_logical():
      """Return the number of logical CPUs in the system."""
      try:
          return os.sysconf("SC_NPROCESSORS_ONLN")
      except ValueError:
          # as a second fallback we try to parse /proc/cpuinfo
          num = 0
          with open('/proc/cpuinfo', 'rb') as f:
              for line in f:
                  if line.lower().startswith(b'processor'):
                      num += 1
  
          # unknown format (e.g. amrel/sparc architectures), see:
          # https://github.com/giampaolo/psutil/issues/200
          # try to parse /proc/stat as a last resort
          if num == 0:
              search = re.compile('cpu\d')
              with open('/proc/stat', 'rt') as f:
                  for line in f:
                      line = line.split(' ')[0]
                      if search.match(line):
                          num += 1
  
          if num == 0:
              # mimic os.cpu_count()
              return None
          return num
  
  
  def cpu_count_physical():
      """Return the number of physical CPUs in the system."""
      with open('/proc/cpuinfo', 'rb') as f:
          found = set()
          for line in f:
              if line.lower().startswith(b'physical id'):
                  found.add(line.strip())
      # mimic os.cpu_count()
      return len(found) if found else None
  
  
  # --- other system functions
  
  def users():
      """Return currently connected users as a list of namedtuples."""
      retlist = []
      rawlist = cext.users()
      for item in rawlist:
          user, tty, hostname, tstamp, user_process = item
          # note: the underlying C function includes entries about
          # system boot, run level and others.  We might want
          # to use them in the future.
          if not user_process:
              continue
          if hostname == ':0.0':
              hostname = 'localhost'
          nt = _common.suser(user, tty or None, hostname, tstamp)
          retlist.append(nt)
      return retlist
  
  
  def boot_time():
      """Return the system boot time expressed in seconds since the epoch."""
      global BOOT_TIME
      with open('/proc/stat', 'rb') as f:
          for line in f:
              if line.startswith(b'btime'):
                  ret = float(line.strip().split()[1])
                  BOOT_TIME = ret
                  return ret
          raise RuntimeError("line 'btime' not found")
  
  
  # --- processes
  
  def pids():
      """Returns a list of PIDs currently running on the system."""
      return [int(x) for x in os.listdir(b'/proc') if x.isdigit()]
  
  
  def pid_exists(pid):
      """Check For the existence of a unix pid."""
      return _psposix.pid_exists(pid)
  
  
  # --- network
  
  class Connections:
      """A wrapper on top of /proc/net/* files, retrieving per-process
      and system-wide open connections (TCP, UDP, UNIX) similarly to
      "netstat -an".
  
      Note: in case of UNIX sockets we're only able to determine the
      local endpoint/path, not the one it's connected to.
      According to [1] it would be possible but not easily.
  
      [1] http://serverfault.com/a/417946
      """
  
      def __init__(self):
          tcp4 = ("tcp", socket.AF_INET, socket.SOCK_STREAM)
          tcp6 = ("tcp6", socket.AF_INET6, socket.SOCK_STREAM)
          udp4 = ("udp", socket.AF_INET, socket.SOCK_DGRAM)
          udp6 = ("udp6", socket.AF_INET6, socket.SOCK_DGRAM)
          unix = ("unix", socket.AF_UNIX, None)
          self.tmap = {
              "all": (tcp4, tcp6, udp4, udp6, unix),
              "tcp": (tcp4, tcp6),
              "tcp4": (tcp4,),
              "tcp6": (tcp6,),
              "udp": (udp4, udp6),
              "udp4": (udp4,),
              "udp6": (udp6,),
              "unix": (unix,),
              "inet": (tcp4, tcp6, udp4, udp6),
              "inet4": (tcp4, udp4),
              "inet6": (tcp6, udp6),
          }
  
      def get_proc_inodes(self, pid):
          inodes = defaultdict(list)
          for fd in os.listdir("/proc/%s/fd" % pid):
              try:
                  inode = os.readlink("/proc/%s/fd/%s" % (pid, fd))
              except OSError:
                  # TODO: need comment here
                  continue
              else:
                  if inode.startswith('socket:['):
                      # the process is using a socket
                      inode = inode[8:][:-1]
                      inodes[inode].append((pid, int(fd)))
          return inodes
  
      def get_all_inodes(self):
          inodes = {}
          for pid in pids():
              try:
                  inodes.update(self.get_proc_inodes(pid))
              except OSError as err:
                  # os.listdir() is gonna raise a lot of access denied
                  # exceptions in case of unprivileged user; that's fine
                  # as we'll just end up returning a connection with PID
                  # and fd set to None anyway.
                  # Both netstat -an and lsof does the same so it's
                  # unlikely we can do any better.
                  # ENOENT just means a PID disappeared on us.
                  if err.errno not in (
                          errno.ENOENT, errno.ESRCH, errno.EPERM, errno.EACCES):
                      raise
          return inodes
  
      def decode_address(self, addr, family):
          """Accept an "ip:port" address as displayed in /proc/net/*
          and convert it into a human readable form, like:
  
          "0500000A:0016" -> ("10.0.0.5", 22)
          "0000000000000000FFFF00000100007F:9E49" -> ("::ffff:127.0.0.1", 40521)
  
          The IP address portion is a little or big endian four-byte
          hexadecimal number; that is, the least significant byte is listed
          first, so we need to reverse the order of the bytes to convert it
          to an IP address.
          The port is represented as a two-byte hexadecimal number.
  
          Reference:
          http://linuxdevcenter.com/pub/a/linux/2000/11/16/LinuxAdmin.html
          """
          ip, port = addr.split(':')
          port = int(port, 16)
          # this usually refers to a local socket in listen mode with
          # no end-points connected
          if not port:
              return ()
          if PY3:
              ip = ip.encode('ascii')
          if family == socket.AF_INET:
              # see: https://github.com/giampaolo/psutil/issues/201
              if sys.byteorder == 'little':
                  ip = socket.inet_ntop(family, base64.b16decode(ip)[::-1])
              else:
                  ip = socket.inet_ntop(family, base64.b16decode(ip))
          else:  # IPv6
              # old version - let's keep it, just in case...
              # ip = ip.decode('hex')
              # return socket.inet_ntop(socket.AF_INET6,
              #          ''.join(ip[i:i+4][::-1] for i in xrange(0, 16, 4)))
              ip = base64.b16decode(ip)
              # see: https://github.com/giampaolo/psutil/issues/201
              if sys.byteorder == 'little':
                  ip = socket.inet_ntop(
                      socket.AF_INET6,
                      struct.pack('>4I', *struct.unpack('<4I', ip)))
              else:
                  ip = socket.inet_ntop(
                      socket.AF_INET6,
                      struct.pack('<4I', *struct.unpack('<4I', ip)))
          return (ip, port)
  
      def process_inet(self, file, family, type_, inodes, filter_pid=None):
          """Parse /proc/net/tcp* and /proc/net/udp* files."""
          if file.endswith('6') and not os.path.exists(file):
              # IPv6 not supported
              return
          with open(file, 'rt') as f:
              f.readline()  # skip the first line
              for line in f:
                  _, laddr, raddr, status, _, _, _, _, _, inode = \
                      line.split()[:10]
                  if inode in inodes:
                      # We assume inet sockets are unique, so we error
                      # out if there are multiple references to the
                      # same inode. We won't do this for UNIX sockets.
                      if len(inodes[inode]) > 1 and family != socket.AF_UNIX:
                          raise ValueError("ambiguos inode with multiple "
                                           "PIDs references")
                      pid, fd = inodes[inode][0]
                  else:
                      pid, fd = None, -1
                  if filter_pid is not None and filter_pid != pid:
                      continue
                  else:
                      if type_ == socket.SOCK_STREAM:
                          status = TCP_STATUSES[status]
                      else:
                          status = _common.CONN_NONE
                      laddr = self.decode_address(laddr, family)
                      raddr = self.decode_address(raddr, family)
                      yield (fd, family, type_, laddr, raddr, status, pid)
  
      def process_unix(self, file, family, inodes, filter_pid=None):
          """Parse /proc/net/unix files."""
          with open(file, 'rt') as f:
              f.readline()  # skip the first line
              for line in f:
                  tokens = line.split()
                  _, _, _, _, type_, _, inode = tokens[0:7]
                  if inode in inodes:
                      # With UNIX sockets we can have a single inode
                      # referencing many file descriptors.
                      pairs = inodes[inode]
                  else:
                      pairs = [(None, -1)]
                  for pid, fd in pairs:
                      if filter_pid is not None and filter_pid != pid:
                          continue
                      else:
                          if len(tokens) == 8:
                              path = tokens[-1]
                          else:
                              path = ""
                          type_ = int(type_)
                          raddr = None
                          status = _common.CONN_NONE
                          yield (fd, family, type_, path, raddr, status, pid)
  
      def retrieve(self, kind, pid=None):
          if kind not in self.tmap:
              raise ValueError("invalid %r kind argument; choose between %s"
                               % (kind, ', '.join([repr(x) for x in self.tmap])))
          if pid is not None:
              inodes = self.get_proc_inodes(pid)
              if not inodes:
                  # no connections for this process
                  return []
          else:
              inodes = self.get_all_inodes()
          ret = []
          for f, family, type_ in self.tmap[kind]:
              if family in (socket.AF_INET, socket.AF_INET6):
                  ls = self.process_inet(
                      "/proc/net/%s" % f, family, type_, inodes, filter_pid=pid)
              else:
                  ls = self.process_unix(
                      "/proc/net/%s" % f, family, inodes, filter_pid=pid)
              for fd, family, type_, laddr, raddr, status, bound_pid in ls:
                  if pid:
                      conn = _common.pconn(fd, family, type_, laddr, raddr,
                                           status)
                  else:
                      conn = _common.sconn(fd, family, type_, laddr, raddr,
                                           status, bound_pid)
                  ret.append(conn)
          return ret
  
  
  _connections = Connections()
  
  
  def net_connections(kind='inet'):
      """Return system-wide open connections."""
      return _connections.retrieve(kind)
  
  
  def net_io_counters():
      """Return network I/O statistics for every network interface
      installed on the system as a dict of raw tuples.
      """
      with open("/proc/net/dev", "rt") as f:
          lines = f.readlines()
      retdict = {}
      for line in lines[2:]:
          colon = line.rfind(':')
          assert colon > 0, repr(line)
          name = line[:colon].strip()
          fields = line[colon + 1:].strip().split()
          bytes_recv = int(fields[0])
          packets_recv = int(fields[1])
          errin = int(fields[2])
          dropin = int(fields[3])
          bytes_sent = int(fields[8])
          packets_sent = int(fields[9])
          errout = int(fields[10])
          dropout = int(fields[11])
          retdict[name] = (bytes_sent, bytes_recv, packets_sent, packets_recv,
                           errin, errout, dropin, dropout)
      return retdict
  
  
  # --- disks
  
  def disk_io_counters():
      """Return disk I/O statistics for every disk installed on the
      system as a dict of raw tuples.
      """
      # man iostat states that sectors are equivalent with blocks and
      # have a size of 512 bytes since 2.4 kernels. This value is
      # needed to calculate the amount of disk I/O in bytes.
      SECTOR_SIZE = 512
  
      # determine partitions we want to look for
      partitions = []
      with open("/proc/partitions", "rt") as f:
          lines = f.readlines()[2:]
      for line in reversed(lines):
          _, _, _, name = line.split()
          if name[-1].isdigit():
              # we're dealing with a partition (e.g. 'sda1'); 'sda' will
              # also be around but we want to omit it
              partitions.append(name)
          else:
              if not partitions or not partitions[-1].startswith(name):
                  # we're dealing with a disk entity for which no
                  # partitions have been defined (e.g. 'sda' but
                  # 'sda1' was not around), see:
                  # https://github.com/giampaolo/psutil/issues/338
                  partitions.append(name)
      #
      retdict = {}
      with open("/proc/diskstats", "rt") as f:
          lines = f.readlines()
      for line in lines:
          # http://www.mjmwired.net/kernel/Documentation/iostats.txt
          fields = line.split()
          if len(fields) > 7:
              _, _, name, reads, _, rbytes, rtime, writes, _, wbytes, wtime = \
                  fields[:11]
          else:
              # from kernel 2.6.0 to 2.6.25
              _, _, name, reads, rbytes, writes, wbytes = fields
              rtime, wtime = 0, 0
          if name in partitions:
              rbytes = int(rbytes) * SECTOR_SIZE
              wbytes = int(wbytes) * SECTOR_SIZE
              reads = int(reads)
              writes = int(writes)
              rtime = int(rtime)
              wtime = int(wtime)
              retdict[name] = (reads, writes, rbytes, wbytes, rtime, wtime)
      return retdict
  
  
  def disk_partitions(all=False):
      """Return mounted disk partitions as a list of nameduples"""
      phydevs = []
      with open("/proc/filesystems", "r") as f:
          for line in f:
              if not line.startswith("nodev"):
                  phydevs.append(line.strip())
  
      retlist = []
      partitions = cext.disk_partitions()
      for partition in partitions:
          device, mountpoint, fstype, opts = partition
          if device == 'none':
              device = ''
          if not all:
              if device == '' or fstype not in phydevs:
                  continue
          ntuple = _common.sdiskpart(device, mountpoint, fstype, opts)
          retlist.append(ntuple)
      return retlist
  
  
  disk_usage = _psposix.disk_usage
  
  
  # --- decorators
  
  def wrap_exceptions(fun):
      """Decorator which translates bare OSError and IOError exceptions
      into NoSuchProcess and AccessDenied.
      """
      @functools.wraps(fun)
      def wrapper(self, *args, **kwargs):
          try:
              return fun(self, *args, **kwargs)
          except EnvironmentError as err:
              # support for private module import
              if NoSuchProcess is None or AccessDenied is None:
                  raise
              # ENOENT (no such file or directory) gets raised on open().
              # ESRCH (no such process) can get raised on read() if
              # process is gone in meantime.
              if err.errno in (errno.ENOENT, errno.ESRCH):
                  raise NoSuchProcess(self.pid, self._name)
              if err.errno in (errno.EPERM, errno.EACCES):
                  raise AccessDenied(self.pid, self._name)
              raise
      return wrapper
  
  
  class Process(object):
      """Linux process implementation."""
  
      __slots__ = ["pid", "_name"]
  
      def __init__(self, pid):
          self.pid = pid
          self._name = None
  
      @wrap_exceptions
      def name(self):
          fname = "/proc/%s/stat" % self.pid
          kw = dict(encoding=DEFAULT_ENCODING) if PY3 else dict()
          with open(fname, "rt", **kw) as f:
              # XXX - gets changed later and probably needs refactoring
              return f.read().split(' ')[1].replace('(', '').replace(')', '')
  
      def exe(self):
          try:
              exe = os.readlink("/proc/%s/exe" % self.pid)
          except (OSError, IOError) as err:
              if err.errno in (errno.ENOENT, errno.ESRCH):
                  # no such file error; might be raised also if the
                  # path actually exists for system processes with
                  # low pids (about 0-20)
                  if os.path.lexists("/proc/%s" % self.pid):
                      return ""
                  else:
                      # ok, it is a process which has gone away
                      raise NoSuchProcess(self.pid, self._name)
              if err.errno in (errno.EPERM, errno.EACCES):
                  raise AccessDenied(self.pid, self._name)
              raise
  
          # readlink() might return paths containing null bytes ('\x00').
          # Certain names have ' (deleted)' appended. Usually this is
          # bogus as the file actually exists. Either way that's not
          # important as we don't want to discriminate executables which
          # have been deleted.
          exe = exe.split('\x00')[0]
          if exe.endswith(' (deleted)') and not os.path.exists(exe):
              exe = exe[:-10]
          return exe
  
      @wrap_exceptions
      def cmdline(self):
          fname = "/proc/%s/cmdline" % self.pid
          kw = dict(encoding=DEFAULT_ENCODING) if PY3 else dict()
          with open(fname, "rt", **kw) as f:
              return [x for x in f.read().split('\x00') if x]
  
      @wrap_exceptions
      def terminal(self):
          tmap = _psposix._get_terminal_map()
          with open("/proc/%s/stat" % self.pid, 'rb') as f:
              tty_nr = int(f.read().split(b' ')[6])
          try:
              return tmap[tty_nr]
          except KeyError:
              return None
  
      if os.path.exists('/proc/%s/io' % os.getpid()):
          @wrap_exceptions
          def io_counters(self):
              fname = "/proc/%s/io" % self.pid
              with open(fname, 'rb') as f:
                  rcount = wcount = rbytes = wbytes = None
                  for line in f:
                      if rcount is None and line.startswith(b"syscr"):
                          rcount = int(line.split()[1])
                      elif wcount is None and line.startswith(b"syscw"):
                          wcount = int(line.split()[1])
                      elif rbytes is None and line.startswith(b"read_bytes"):
                          rbytes = int(line.split()[1])
                      elif wbytes is None and line.startswith(b"write_bytes"):
                          wbytes = int(line.split()[1])
                  for x in (rcount, wcount, rbytes, wbytes):
                      if x is None:
                          raise NotImplementedError(
                              "couldn't read all necessary info from %r" % fname)
                  return _common.pio(rcount, wcount, rbytes, wbytes)
      else:
          def io_counters(self):
              raise NotImplementedError("couldn't find /proc/%s/io (kernel "
                                        "too old?)" % self.pid)
  
      @wrap_exceptions
      def cpu_times(self):
          with open("/proc/%s/stat" % self.pid, 'rb') as f:
              st = f.read().strip()
          # ignore the first two values ("pid (exe)")
          st = st[st.find(b')') + 2:]
          values = st.split(b' ')
          utime = float(values[11]) / CLOCK_TICKS
          stime = float(values[12]) / CLOCK_TICKS
          return _common.pcputimes(utime, stime)
  
      @wrap_exceptions
      def wait(self, timeout=None):
          try:
              return _psposix.wait_pid(self.pid, timeout)
          except _psposix.TimeoutExpired:
              # support for private module import
              if TimeoutExpired is None:
                  raise
              raise TimeoutExpired(timeout, self.pid, self._name)
  
      @wrap_exceptions
      def create_time(self):
          with open("/proc/%s/stat" % self.pid, 'rb') as f:
              st = f.read().strip()
          # ignore the first two values ("pid (exe)")
          st = st[st.rfind(b')') + 2:]
          values = st.split(b' ')
          # According to documentation, starttime is in field 21 and the
          # unit is jiffies (clock ticks).
          # We first divide it for clock ticks and then add uptime returning
          # seconds since the epoch, in UTC.
          # Also use cached value if available.
          bt = BOOT_TIME or boot_time()
          return (float(values[19]) / CLOCK_TICKS) + bt
  
      @wrap_exceptions
      def memory_info(self):
          with open("/proc/%s/statm" % self.pid, 'rb') as f:
              vms, rss = f.readline().split()[:2]
              return _common.pmem(int(rss) * PAGESIZE,
                                  int(vms) * PAGESIZE)
  
      @wrap_exceptions
      def memory_info_ex(self):
          #  ============================================================
          # | FIELD  | DESCRIPTION                         | AKA  | TOP  |
          #  ============================================================
          # | rss    | resident set size                   |      | RES  |
          # | vms    | total program size                  | size | VIRT |
          # | shared | shared pages (from shared mappings) |      | SHR  |
          # | text   | text ('code')                       | trs  | CODE |
          # | lib    | library (unused in Linux 2.6)       | lrs  |      |
          # | data   | data + stack                        | drs  | DATA |
          # | dirty  | dirty pages (unused in Linux 2.6)   | dt   |      |
          #  ============================================================
          with open("/proc/%s/statm" % self.pid, "rb") as f:
              vms, rss, shared, text, lib, data, dirty = \
                  [int(x) * PAGESIZE for x in f.readline().split()[:7]]
          return pextmem(rss, vms, shared, text, lib, data, dirty)
  
      if os.path.exists('/proc/%s/smaps' % os.getpid()):
  
          @wrap_exceptions
          def memory_maps(self):
              """Return process's mapped memory regions as a list of nameduples.
              Fields are explained in 'man proc'; here is an updated (Apr 2012)
              version: http://goo.gl/fmebo
              """
              with open("/proc/%s/smaps" % self.pid, "rt") as f:
                  first_line = f.readline()
                  current_block = [first_line]
  
                  def get_blocks():
                      data = {}
                      for line in f:
                          fields = line.split(None, 5)
                          if not fields[0].endswith(':'):
                              # new block section
                              yield (current_block.pop(), data)
                              current_block.append(line)
                          else:
                              try:
                                  data[fields[0]] = int(fields[1]) * 1024
                              except ValueError:
                                  if fields[0].startswith('VmFlags:'):
                                      # see issue #369
                                      continue
                                  else:
                                      raise ValueError("don't know how to inte"
                                                       "rpret line %r" % line)
                      yield (current_block.pop(), data)
  
                  ls = []
                  if first_line:  # smaps file can be empty
                      for header, data in get_blocks():
                          hfields = header.split(None, 5)
                          try:
                              addr, perms, offset, dev, inode, path = hfields
                          except ValueError:
                              addr, perms, offset, dev, inode, path = \
                                  hfields + ['']
                          if not path:
                              path = '[anon]'
                          else:
                              path = path.strip()
                          ls.append((
                              addr, perms, path,
                              data['Rss:'],
                              data.get('Size:', 0),
                              data.get('Pss:', 0),
                              data.get('Shared_Clean:', 0),
                              data.get('Shared_Dirty:', 0),
                              data.get('Private_Clean:', 0),
                              data.get('Private_Dirty:', 0),
                              data.get('Referenced:', 0),
                              data.get('Anonymous:', 0),
                              data.get('Swap:', 0)
                          ))
              return ls
  
      else:
          def memory_maps(self):
              msg = "couldn't find /proc/%s/smaps; kernel < 2.6.14 or "  \
                    "CONFIG_MMU kernel configuration option is not enabled" \
                    % self.pid
              raise NotImplementedError(msg)
  
      @wrap_exceptions
      def cwd(self):
          # readlink() might return paths containing null bytes causing
          # problems when used with other fs-related functions (os.*,
          # open(), ...)
          path = os.readlink("/proc/%s/cwd" % self.pid)
          return path.replace('\x00', '')
  
      @wrap_exceptions
      def num_ctx_switches(self):
          vol = unvol = None
          with open("/proc/%s/status" % self.pid, "rb") as f:
              for line in f:
                  if line.startswith(b"voluntary_ctxt_switches"):
                      vol = int(line.split()[1])
                  elif line.startswith(b"nonvoluntary_ctxt_switches"):
                      unvol = int(line.split()[1])
                  if vol is not None and unvol is not None:
                      return _common.pctxsw(vol, unvol)
              raise NotImplementedError(
                  "'voluntary_ctxt_switches' and 'nonvoluntary_ctxt_switches'"
                  "fields were not found in /proc/%s/status; the kernel is "
                  "probably older than 2.6.23" % self.pid)
  
      @wrap_exceptions
      def num_threads(self):
          with open("/proc/%s/status" % self.pid, "rb") as f:
              for line in f:
                  if line.startswith(b"Threads:"):
                      return int(line.split()[1])
              raise NotImplementedError("line not found")
  
      @wrap_exceptions
      def threads(self):
          thread_ids = os.listdir("/proc/%s/task" % self.pid)
          thread_ids.sort()
          retlist = []
          hit_enoent = False
          for thread_id in thread_ids:
              fname = "/proc/%s/task/%s/stat" % (self.pid, thread_id)
              try:
                  with open(fname, 'rb') as f:
                      st = f.read().strip()
              except EnvironmentError as err:
                  if err.errno == errno.ENOENT:
                      # no such file or directory; it means thread
                      # disappeared on us
                      hit_enoent = True
                      continue
                  raise
              # ignore the first two values ("pid (exe)")
              st = st[st.find(b')') + 2:]
              values = st.split(b' ')
              utime = float(values[11]) / CLOCK_TICKS
              stime = float(values[12]) / CLOCK_TICKS
              ntuple = _common.pthread(int(thread_id), utime, stime)
              retlist.append(ntuple)
          if hit_enoent:
              # raise NSP if the process disappeared on us
              os.stat('/proc/%s' % self.pid)
          return retlist
  
      @wrap_exceptions
      def nice_get(self):
          # with open('/proc/%s/stat' % self.pid, 'r') as f:
          #   data = f.read()
          #   return int(data.split()[18])
  
          # Use C implementation
          return _psutil_posix.getpriority(self.pid)
  
      @wrap_exceptions
      def nice_set(self, value):
          return _psutil_posix.setpriority(self.pid, value)
  
      @wrap_exceptions
      def cpu_affinity_get(self):
          return cext.proc_cpu_affinity_get(self.pid)
  
      @wrap_exceptions
      def cpu_affinity_set(self, cpus):
          try:
              cext.proc_cpu_affinity_set(self.pid, cpus)
          except OSError as err:
              if err.errno == errno.EINVAL:
                  allcpus = tuple(range(len(per_cpu_times())))
                  for cpu in cpus:
                      if cpu not in allcpus:
                          raise ValueError("invalid CPU #%i (choose between %s)"
                                           % (cpu, allcpus))
              raise
  
      # only starting from kernel 2.6.13
      if hasattr(cext, "proc_ioprio_get"):
  
          @wrap_exceptions
          def ionice_get(self):
              ioclass, value = cext.proc_ioprio_get(self.pid)
              return _common.pionice(ioclass, value)
  
          @wrap_exceptions
          def ionice_set(self, ioclass, value):
              if ioclass in (IOPRIO_CLASS_NONE, None):
                  if value:
                      msg = "can't specify value with IOPRIO_CLASS_NONE"
                      raise ValueError(msg)
                  ioclass = IOPRIO_CLASS_NONE
                  value = 0
              if ioclass in (IOPRIO_CLASS_RT, IOPRIO_CLASS_BE):
                  if value is None:
                      value = 4
              elif ioclass == IOPRIO_CLASS_IDLE:
                  if value:
                      msg = "can't specify value with IOPRIO_CLASS_IDLE"
                      raise ValueError(msg)
                  value = 0
              else:
                  value = 0
              if not 0 <= value <= 8:
                  raise ValueError(
                      "value argument range expected is between 0 and 8")
              return cext.proc_ioprio_set(self.pid, ioclass, value)
  
      if HAS_PRLIMIT:
          @wrap_exceptions
          def rlimit(self, resource, limits=None):
              # if pid is 0 prlimit() applies to the calling process and
              # we don't want that
              if self.pid == 0:
                  raise ValueError("can't use prlimit() against PID 0 process")
              if limits is None:
                  # get
                  return cext.linux_prlimit(self.pid, resource)
              else:
                  # set
                  if len(limits) != 2:
                      raise ValueError(
                          "second argument must be a (soft, hard) tuple")
                  soft, hard = limits
                  cext.linux_prlimit(self.pid, resource, soft, hard)
  
      @wrap_exceptions
      def status(self):
          with open("/proc/%s/status" % self.pid, 'rb') as f:
              for line in f:
                  if line.startswith(b"State:"):
                      letter = line.split()[1]
                      if PY3:
                          letter = letter.decode()
                      # XXX is '?' legit? (we're not supposed to return
                      # it anyway)
                      return PROC_STATUSES.get(letter, '?')
  
      @wrap_exceptions
      def open_files(self):
          retlist = []
          files = os.listdir("/proc/%s/fd" % self.pid)
          hit_enoent = False
          for fd in files:
              file = "/proc/%s/fd/%s" % (self.pid, fd)
              try:
                  file = os.readlink(file)
              except OSError as err:
                  # ENOENT == file which is gone in the meantime
                  if err.errno in (errno.ENOENT, errno.ESRCH):
                      hit_enoent = True
                      continue
                  elif err.errno == errno.EINVAL:
                      # not a link
                      continue
                  else:
                      raise
              else:
                  # If file is not an absolute path there's no way
                  # to tell whether it's a regular file or not,
                  # so we skip it. A regular file is always supposed
                  # to be absolutized though.
                  if file.startswith('/') and isfile_strict(file):
                      ntuple = _common.popenfile(file, int(fd))
                      retlist.append(ntuple)
          if hit_enoent:
              # raise NSP if the process disappeared on us
              os.stat('/proc/%s' % self.pid)
          return retlist
  
      @wrap_exceptions
      def connections(self, kind='inet'):
          ret = _connections.retrieve(kind, self.pid)
          # raise NSP if the process disappeared on us
          os.stat('/proc/%s' % self.pid)
          return ret
  
      @wrap_exceptions
      def num_fds(self):
          return len(os.listdir("/proc/%s/fd" % self.pid))
  
      @wrap_exceptions
      def ppid(self):
          with open("/proc/%s/status" % self.pid, 'rb') as f:
              for line in f:
                  if line.startswith(b"PPid:"):
                      # PPid: nnnn
                      return int(line.split()[1])
              raise NotImplementedError("line not found")
  
      @wrap_exceptions
      def uids(self):
          with open("/proc/%s/status" % self.pid, 'rb') as f:
              for line in f:
                  if line.startswith(b'Uid:'):
                      _, real, effective, saved, fs = line.split()
                      return _common.puids(int(real), int(effective), int(saved))
              raise NotImplementedError("line not found")
  
      @wrap_exceptions
      def gids(self):
          with open("/proc/%s/status" % self.pid, 'rb') as f:
              for line in f:
                  if line.startswith(b'Gid:'):
                      _, real, effective, saved, fs = line.split()
                      return _common.pgids(int(real), int(effective), int(saved))
              raise NotImplementedError("line not found")
  