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1"""Posix-specific implementation of process utilities.
3This file is only meant to be imported by process.py, not by end-users.
4"""
6#-----------------------------------------------------------------------------
7# Copyright (C) 2010-2011 The IPython Development Team
8#
9# Distributed under the terms of the BSD License. The full license is in
10# the file COPYING, distributed as part of this software.
11#-----------------------------------------------------------------------------
13#-----------------------------------------------------------------------------
14# Imports
15#-----------------------------------------------------------------------------
17# Stdlib
18import errno
19import os
20import subprocess as sp
21import sys
23# Our own
24from ._process_common import getoutput, arg_split
25from IPython.utils.encoding import DEFAULT_ENCODING
27#-----------------------------------------------------------------------------
28# Function definitions
29#-----------------------------------------------------------------------------
31class ProcessHandler(object):
32 """Execute subprocesses under the control of pexpect.
33 """
34 # Timeout in seconds to wait on each reading of the subprocess' output.
35 # This should not be set too low to avoid cpu overusage from our side,
36 # since we read in a loop whose period is controlled by this timeout.
37 read_timeout = 0.05
39 # Timeout to give a process if we receive SIGINT, between sending the
40 # SIGINT to the process and forcefully terminating it.
41 terminate_timeout = 0.2
43 # File object where stdout and stderr of the subprocess will be written
44 logfile = None
46 # Shell to call for subprocesses to execute
47 _sh = None
49 @property
50 def sh(self):
51 if self._sh is None:
52 import pexpect
53 shell_name = os.environ.get("SHELL", "sh")
54 self._sh = pexpect.which(shell_name)
55 if self._sh is None:
56 raise OSError('"{}" shell not found'.format(shell_name))
58 return self._sh
60 def __init__(self, logfile=None, read_timeout=None, terminate_timeout=None):
61 """Arguments are used for pexpect calls."""
62 self.read_timeout = (ProcessHandler.read_timeout if read_timeout is
63 None else read_timeout)
64 self.terminate_timeout = (ProcessHandler.terminate_timeout if
65 terminate_timeout is None else
66 terminate_timeout)
67 self.logfile = sys.stdout if logfile is None else logfile
69 def getoutput(self, cmd):
70 """Run a command and return its stdout/stderr as a string.
72 Parameters
73 ----------
74 cmd : str
75 A command to be executed in the system shell.
77 Returns
78 -------
79 output : str
80 A string containing the combination of stdout and stderr from the
81 subprocess, in whatever order the subprocess originally wrote to its
82 file descriptors (so the order of the information in this string is the
83 correct order as would be seen if running the command in a terminal).
84 """
85 import pexpect
86 try:
87 return pexpect.run(self.sh, args=['-c', cmd]).replace('\r\n', '\n')
88 except KeyboardInterrupt:
89 print('^C', file=sys.stderr, end='')
91 def getoutput_pexpect(self, cmd):
92 """Run a command and return its stdout/stderr as a string.
94 Parameters
95 ----------
96 cmd : str
97 A command to be executed in the system shell.
99 Returns
100 -------
101 output : str
102 A string containing the combination of stdout and stderr from the
103 subprocess, in whatever order the subprocess originally wrote to its
104 file descriptors (so the order of the information in this string is the
105 correct order as would be seen if running the command in a terminal).
106 """
107 import pexpect
108 try:
109 return pexpect.run(self.sh, args=['-c', cmd]).replace('\r\n', '\n')
110 except KeyboardInterrupt:
111 print('^C', file=sys.stderr, end='')
113 def system(self, cmd):
114 """Execute a command in a subshell.
116 Parameters
117 ----------
118 cmd : str
119 A command to be executed in the system shell.
121 Returns
122 -------
123 int : child's exitstatus
124 """
125 import pexpect
127 # Get likely encoding for the output.
128 enc = DEFAULT_ENCODING
130 # Patterns to match on the output, for pexpect. We read input and
131 # allow either a short timeout or EOF
132 patterns = [pexpect.TIMEOUT, pexpect.EOF]
133 # the index of the EOF pattern in the list.
134 # even though we know it's 1, this call means we don't have to worry if
135 # we change the above list, and forget to change this value:
136 EOF_index = patterns.index(pexpect.EOF)
137 # The size of the output stored so far in the process output buffer.
138 # Since pexpect only appends to this buffer, each time we print we
139 # record how far we've printed, so that next time we only print *new*
140 # content from the buffer.
141 out_size = 0
142 try:
143 # Since we're not really searching the buffer for text patterns, we
144 # can set pexpect's search window to be tiny and it won't matter.
145 # We only search for the 'patterns' timeout or EOF, which aren't in
146 # the text itself.
147 #child = pexpect.spawn(pcmd, searchwindowsize=1)
148 if hasattr(pexpect, 'spawnb'):
149 child = pexpect.spawnb(self.sh, args=['-c', cmd]) # Pexpect-U
150 else:
151 child = pexpect.spawn(self.sh, args=['-c', cmd]) # Vanilla Pexpect
152 flush = sys.stdout.flush
153 while True:
154 # res is the index of the pattern that caused the match, so we
155 # know whether we've finished (if we matched EOF) or not
156 res_idx = child.expect_list(patterns, self.read_timeout)
157 print(child.before[out_size:].decode(enc, 'replace'), end='')
158 flush()
159 if res_idx==EOF_index:
160 break
161 # Update the pointer to what we've already printed
162 out_size = len(child.before)
163 except KeyboardInterrupt:
164 # We need to send ^C to the process. The ascii code for '^C' is 3
165 # (the character is known as ETX for 'End of Text', see
166 # curses.ascii.ETX).
167 child.sendline(chr(3))
168 # Read and print any more output the program might produce on its
169 # way out.
170 try:
171 out_size = len(child.before)
172 child.expect_list(patterns, self.terminate_timeout)
173 print(child.before[out_size:].decode(enc, 'replace'), end='')
174 sys.stdout.flush()
175 except KeyboardInterrupt:
176 # Impatient users tend to type it multiple times
177 pass
178 finally:
179 # Ensure the subprocess really is terminated
180 child.terminate(force=True)
181 # add isalive check, to ensure exitstatus is set:
182 child.isalive()
184 # We follow the subprocess pattern, returning either the exit status
185 # as a positive number, or the terminating signal as a negative
186 # number.
187 # on Linux, sh returns 128+n for signals terminating child processes on Linux
188 # on BSD (OS X), the signal code is set instead
189 if child.exitstatus is None:
190 # on WIFSIGNALED, pexpect sets signalstatus, leaving exitstatus=None
191 if child.signalstatus is None:
192 # this condition may never occur,
193 # but let's be certain we always return an integer.
194 return 0
195 return -child.signalstatus
196 if child.exitstatus > 128:
197 return -(child.exitstatus - 128)
198 return child.exitstatus
201# Make system() with a functional interface for outside use. Note that we use
202# getoutput() from the _common utils, which is built on top of popen(). Using
203# pexpect to get subprocess output produces difficult to parse output, since
204# programs think they are talking to a tty and produce highly formatted output
205# (ls is a good example) that makes them hard.
206system = ProcessHandler().system
208def check_pid(pid):
209 try:
210 os.kill(pid, 0)
211 except OSError as err:
212 if err.errno == errno.ESRCH:
213 return False
214 elif err.errno == errno.EPERM:
215 # Don't have permission to signal the process - probably means it exists
216 return True
217 raise
218 else:
219 return True