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"""Posix-specific implementation of process utilities.
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This file is only meant to be imported by process.py, not by end-users.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2010-2011 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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# Stdlib
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import errno
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import os
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import subprocess as sp
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import sys
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import pexpect
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# Our own
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from ._process_common import getoutput, arg_split
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from IPython.utils.encoding import DEFAULT_ENCODING
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#-----------------------------------------------------------------------------
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# Function definitions
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#-----------------------------------------------------------------------------
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class ProcessHandler(object):
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"""Execute subprocesses under the control of pexpect.
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"""
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# Timeout in seconds to wait on each reading of the subprocess' output.
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# This should not be set too low to avoid cpu overusage from our side,
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# since we read in a loop whose period is controlled by this timeout.
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read_timeout = 0.05
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# Timeout to give a process if we receive SIGINT, between sending the
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# SIGINT to the process and forcefully terminating it.
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terminate_timeout = 0.2
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# File object where stdout and stderr of the subprocess will be written
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logfile = None
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# Shell to call for subprocesses to execute
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_sh = None
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@property
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def sh(self):
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if self._sh is None:
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shell_name = os.environ.get("SHELL", "sh")
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self._sh = pexpect.which(shell_name)
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if self._sh is None:
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raise OSError('"{}" shell not found'.format(shell_name))
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return self._sh
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def __init__(self, logfile=None, read_timeout=None, terminate_timeout=None):
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"""Arguments are used for pexpect calls."""
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self.read_timeout = (ProcessHandler.read_timeout if read_timeout is
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None else read_timeout)
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self.terminate_timeout = (ProcessHandler.terminate_timeout if
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terminate_timeout is None else
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terminate_timeout)
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self.logfile = sys.stdout if logfile is None else logfile
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def getoutput(self, cmd):
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"""Run a command and return its stdout/stderr as a string.
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Parameters
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----------
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cmd : str
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A command to be executed in the system shell.
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Returns
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-------
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output : str
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A string containing the combination of stdout and stderr from the
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subprocess, in whatever order the subprocess originally wrote to its
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file descriptors (so the order of the information in this string is the
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correct order as would be seen if running the command in a terminal).
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"""
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try:
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return pexpect.run(self.sh, args=['-c', cmd]).replace('\r\n', '\n')
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except KeyboardInterrupt:
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print('^C', file=sys.stderr, end='')
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def getoutput_pexpect(self, cmd):
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"""Run a command and return its stdout/stderr as a string.
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Parameters
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----------
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cmd : str
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A command to be executed in the system shell.
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Returns
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-------
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output : str
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A string containing the combination of stdout and stderr from the
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subprocess, in whatever order the subprocess originally wrote to its
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file descriptors (so the order of the information in this string is the
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correct order as would be seen if running the command in a terminal).
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"""
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try:
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return pexpect.run(self.sh, args=['-c', cmd]).replace('\r\n', '\n')
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except KeyboardInterrupt:
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print('^C', file=sys.stderr, end='')
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def system(self, cmd):
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"""Execute a command in a subshell.
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Parameters
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----------
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cmd : str
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A command to be executed in the system shell.
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Returns
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-------
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int : child's exitstatus
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"""
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# Get likely encoding for the output.
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enc = DEFAULT_ENCODING
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# Patterns to match on the output, for pexpect. We read input and
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# allow either a short timeout or EOF
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patterns = [pexpect.TIMEOUT, pexpect.EOF]
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# the index of the EOF pattern in the list.
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# even though we know it's 1, this call means we don't have to worry if
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# we change the above list, and forget to change this value:
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EOF_index = patterns.index(pexpect.EOF)
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# The size of the output stored so far in the process output buffer.
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# Since pexpect only appends to this buffer, each time we print we
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# record how far we've printed, so that next time we only print *new*
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# content from the buffer.
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out_size = 0
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try:
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# Since we're not really searching the buffer for text patterns, we
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# can set pexpect's search window to be tiny and it won't matter.
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# We only search for the 'patterns' timeout or EOF, which aren't in
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# the text itself.
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#child = pexpect.spawn(pcmd, searchwindowsize=1)
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if hasattr(pexpect, 'spawnb'):
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child = pexpect.spawnb(self.sh, args=['-c', cmd]) # Pexpect-U
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else:
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child = pexpect.spawn(self.sh, args=['-c', cmd]) # Vanilla Pexpect
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flush = sys.stdout.flush
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while True:
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# res is the index of the pattern that caused the match, so we
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# know whether we've finished (if we matched EOF) or not
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res_idx = child.expect_list(patterns, self.read_timeout)
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print(child.before[out_size:].decode(enc, 'replace'), end='')
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flush()
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if res_idx==EOF_index:
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break
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# Update the pointer to what we've already printed
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out_size = len(child.before)
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except KeyboardInterrupt:
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# We need to send ^C to the process. The ascii code for '^C' is 3
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# (the character is known as ETX for 'End of Text', see
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# curses.ascii.ETX).
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child.sendline(chr(3))
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# Read and print any more output the program might produce on its
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# way out.
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try:
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out_size = len(child.before)
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child.expect_list(patterns, self.terminate_timeout)
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print(child.before[out_size:].decode(enc, 'replace'), end='')
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sys.stdout.flush()
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except KeyboardInterrupt:
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# Impatient users tend to type it multiple times
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pass
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finally:
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# Ensure the subprocess really is terminated
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child.terminate(force=True)
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# add isalive check, to ensure exitstatus is set:
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child.isalive()
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# We follow the subprocess pattern, returning either the exit status
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# as a positive number, or the terminating signal as a negative
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# number.
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# on Linux, sh returns 128+n for signals terminating child processes on Linux
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# on BSD (OS X), the signal code is set instead
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if child.exitstatus is None:
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# on WIFSIGNALED, pexpect sets signalstatus, leaving exitstatus=None
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if child.signalstatus is None:
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# this condition may never occur,
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# but let's be certain we always return an integer.
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return 0
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return -child.signalstatus
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if child.exitstatus > 128:
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return -(child.exitstatus - 128)
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return child.exitstatus
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# Make system() with a functional interface for outside use. Note that we use
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# getoutput() from the _common utils, which is built on top of popen(). Using
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# pexpect to get subprocess output produces difficult to parse output, since
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# programs think they are talking to a tty and produce highly formatted output
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# (ls is a good example) that makes them hard.
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system = ProcessHandler().system
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def check_pid(pid):
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try:
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os.kill(pid, 0)
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except OSError as err:
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if err.errno == errno.ESRCH:
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return False
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elif err.errno == errno.EPERM:
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# Don't have permission to signal the process - probably means it exists
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return True
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raise
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else:
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return True
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