paramiko_hostname

#!/usr/bin/env python3

import os
import socket
import logging
import paramiko
import argparse


def create_ssh_client(hostname):
    """Create a paramiko ssh_client object for a 'hostname' that is defined on
    the ~/.ssh/config file and ssh keys are used to authenticate"""
    config = paramiko.config.SSHConfig()
    config.parse(open(os.path.expanduser('~/.ssh/config')))
    host = config.lookup(hostname)
    params = {}
    params["timeout"] = 5
    for key in host.keys():
        if key == "hostname":
            params[key] = host[key]
        elif key == "user":
            params["username"] = host[key]
        elif key == "port":
            params[key] = int(host[key])
        elif key == "identityfile":
            params["key_filename"] = host[key][0]
    client = paramiko.SSHClient()
    client.load_system_host_keys()
    client.set_missing_host_key_policy(paramiko.RejectPolicy())
    try:
        client.connect(**params)
    except socket.timeout:
        logging.error("Connection timed out for host '{0}'"
                      .format(hostname))
        return None
    except socket.gaierror:
        logging.exception("Connection error: if [Errno -2] the host '{0}'"
                          "is not found in ssh_config\n".format(hostname))
        return None
    except paramiko.SSHException as e:
        logging.exception("Connection error on '{0}': {1}".format(hostname, e))
        return None
    return client


def check_remote_hostname(remote):
    ssh_client = create_ssh_client(remote)
    stdin, stdout, stderr = ssh_client.exec_command('hostname')
    if stdout.channel.recv_exit_status() == 0:
        out = stdout.readlines()
        print(out[0])
    else:
        print("Error running 'hostname' command on {0}".format(remote))


if __name__ == '__main__':

    parser = argparse.ArgumentParser(
        description='Print a remote ssh server hostname (ssh authentication'
                    ' already setup on ssh_config)')
    parser.add_argument('server', type=str, help='remote server hostname as'
                        ' in your ssh_config')
    args = parser.parse_args()
    remote = args.server

    check_remote_hostname(remote)