environment/lib/python2.7/site-packages/IPython/utils/_process_posix.py
def system(self, cmd):
        """Execute a command in a subshell.

        Parameters
        ----------
        cmd : str
          A command to be executed in the system shell.

        Returns
        -------
        int : child's exitstatus
        """
        # Get likely encoding for the output.
        enc = DEFAULT_ENCODING
        
        # Patterns to match on the output, for pexpect.  We read input and
        # allow either a short timeout or EOF
        patterns = [pexpect.TIMEOUT, pexpect.EOF]
        # the index of the EOF pattern in the list.
        # even though we know it's 1, this call means we don't have to worry if
        # we change the above list, and forget to change this value:
        EOF_index = patterns.index(pexpect.EOF)
        # The size of the output stored so far in the process output buffer.
        # Since pexpect only appends to this buffer, each time we print we
        # record how far we've printed, so that next time we only print *new*
        # content from the buffer.
        out_size = 0
        try:
            # Since we're not really searching the buffer for text patterns, we
            # can set pexpect's search window to be tiny and it won't matter.
            # We only search for the 'patterns' timeout or EOF, which aren't in
            # the text itself.
            #child = pexpect.spawn(pcmd, searchwindowsize=1)
            if hasattr(pexpect, 'spawnb'):
                child = pexpect.spawnb(self.sh, args=['-c', cmd]) # Pexpect-U
            else:
                child = pexpect.spawn(self.sh, args=['-c', cmd])  # Vanilla Pexpect
            flush = sys.stdout.flush
            while True:
                # res is the index of the pattern that caused the match, so we
                # know whether we've finished (if we matched EOF) or not
                res_idx = child.expect_list(patterns, self.read_timeout)
                print(child.before[out_size:].decode(enc, 'replace'), end='')
                flush()
                if res_idx==EOF_index:
                    break
                # Update the pointer to what we've already printed
                out_size = len(child.before)
        except KeyboardInterrupt:
            # We need to send ^C to the process.  The ascii code for '^C' is 3
            # (the character is known as ETX for 'End of Text', see
            # curses.ascii.ETX).
            child.sendline(chr(3))
            # Read and print any more output the program might produce on its
            # way out.
            try:
                out_size = len(child.before)
                child.expect_list(patterns, self.terminate_timeout)
                print(child.before[out_size:].decode(enc, 'replace'), end='')
                sys.stdout.flush()
            except KeyboardInterrupt:
                # Impatient users tend to type it multiple times
                pass
            finally:
                # Ensure the subprocess really is terminated
                child.terminate(force=True)
        # add isalive check, to ensure exitstatus is set:
        child.isalive()
        return child.exitstatus
def system(self, cmd):
        """Execute a command in a subshell.

        Parameters
        ----------
        cmd : str
          A command to be executed in the system shell.

        Returns
        -------
        int : child's exitstatus
        """
        # Get likely encoding for the output.
        enc = DEFAULT_ENCODING
        
        # Patterns to match on the output, for pexpect.  We read input and
        # allow either a short timeout or EOF
        patterns = [pexpect.TIMEOUT, pexpect.EOF]
        # the index of the EOF pattern in the list.
        # even though we know it's 1, this call means we don't have to worry if
        # we change the above list, and forget to change this value:
        EOF_index = patterns.index(pexpect.EOF)
        # The size of the output stored so far in the process output buffer.
        # Since pexpect only appends to this buffer, each time we print we
        # record how far we've printed, so that next time we only print *new*
        # content from the buffer.
        out_size = 0
        try:
            # Since we're not really searching the buffer for text patterns, we
            # can set pexpect's search window to be tiny and it won't matter.
            # We only search for the 'patterns' timeout or EOF, which aren't in
            # the text itself.
            #child = pexpect.spawn(pcmd, searchwindowsize=1)
            if hasattr(pexpect, 'spawnb'):
                child = pexpect.spawnb(self.sh, args=['-c', cmd]) # Pexpect-U
            else:
                child = pexpect.spawn(self.sh, args=['-c', cmd])  # Vanilla Pexpect
            flush = sys.stdout.flush
            while True:
                # res is the index of the pattern that caused the match, so we
                # know whether we've finished (if we matched EOF) or not
                res_idx = child.expect_list(patterns, self.read_timeout)
                print(child.before[out_size:].decode(enc, 'replace'), end='')
                flush()
                if res_idx==EOF_index:
                    break
                # Update the pointer to what we've already printed
                out_size = len(child.before)
        except KeyboardInterrupt:
            # We need to send ^C to the process.  The ascii code for '^C' is 3
            # (the character is known as ETX for 'End of Text', see
            # curses.ascii.ETX).
            child.sendline(chr(3))
            # Read and print any more output the program might produce on its
            # way out.
            try:
                out_size = len(child.before)
                child.expect_list(patterns, self.terminate_timeout)
                print(child.before[out_size:].decode(enc, 'replace'), end='')
                sys.stdout.flush()
            except KeyboardInterrupt:
                # Impatient users tend to type it multiple times
                pass
            finally:
                # Ensure the subprocess really is terminated
                child.terminate(force=True)
        # add isalive check, to ensure exitstatus is set:
        child.isalive()
        return child.exitstatus
Execute a command in a subshell.

        Parameters
        ----------
        cmd : str
          A command to be executed in the system shell.

        Returns
        -------
        int : child's exitstatus