Mini Shell

"""Convenience classes for paramiko"""
import stat
import paramiko
from rads.exceptions import SSHError

class SSHConn(paramiko.SSHClient):
    """Context manager that handles SSH connections.
    Most exceptions may raise SSHError, but accessing the sftp attribute or
    paramiko functions inherited from paramiko.SSHClient directly may raise
    socket.error or paramiko.ssh_exception.SSHException"""
    def __init__(self, sftp, **kwargs):
        """Args for the context manager are read from here.
        If you don't need sftp functionality, set sftp=False"""
        super(SSHConn, self).__init__()
        self.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        self._kwargs = kwargs
        self._use_sftp = sftp
        self.sftp = None
    def __enter__(self):
        """Connects to SSH using the context manager 'with' statement"""
        try:
            self.connect(**self._kwargs)
            if self._use_sftp:
                self.sftp = self.open_sftp()
        except Exception as exc:
            raise SSHError(exc)
        return self
    def __exit__(self, exc_type, exc_val, traceback):
        """Disconnects from SSH on un-indent, even if an exception is raised"""
        if self._use_sftp:
            self.sftp.close()
        self.close()
    def listdir(self, path, _type=None):
        """List contents of a remote dir similar to os.listdir()"""
        try:
            items = []
            for lstat in self.sftp.listdir_iter(path):
                if _type is None or _type(lstat.st_mode):
                    items.append(lstat.filename)
            return items
        except Exception as exc:
            raise SSHError(exc)
    def ls_dirs(self, path):
        """listdir() but only folders"""
        return self.listdir(path, _type=stat.S_ISDIR)
    def ls_files(self, path):
        """listdir() but only files"""
        return self.listdir(path, _type=stat.S_ISREG)
    def run(self, cmd):
        """Execute a command and return a CmdResult object"""
        try:
            return CmdResult(self, cmd)
        except Exception as exc:
            raise SSHError(exc)

class CmdResult(object):
    """Holds a command result"""
    def __init__(self, conn, cmd):
        chan = conn.get_transport().open_session()
        chan.set_environment_variable('shell', 'xterm')
        chan.exec_command(cmd)
        stdout = chan.makefile('rb', -1)
        stderr = chan.makefile_stderr('rb', -1)
        self.stdout = stdout.read()
        self.stderr = stderr.read()
        if self.stderr.startswith('stdin: is not a tty\n'):
            # this is caused by 'mesg y' in /etc/bashrc. Using a pty would
            # avoid that, but then mix stdout and stderr which is not wanted.
            self.stderr = self.stderr[20:]
        self.rcode = chan.recv_exit_status()
        chan.close()