Paramiko: read from standard output of remotely executed command

Question

so I was working with paramiko for some basic SSH testing and I'm not getting any output into stdout. Heres my code.

import paramiko
client=paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
com="ls ~/desktop"
client.connect('MyIPAddress',MyPortNumber, username='username', password='password')
output=""
stdin, stdout, stderr = client.exec_command(com)

print "ssh succuessful. Closing connection"
client.close()
print "Connection closed"
stdout=stdout.readlines()
print stdout
print com
for line in stdout:
    output=output+line
if output!="":
    print output
else:
    print "There was no output for this command"

So whenever I run this, the command is executed (as seen by if I do something like a cp, the file is copied), but I always get "There was no output for this command". When stdout=stdout.readlines() is printed, [] is the output. In addition, if I add a print statement into the for loop, it never gets run. Could someone help me out here? Thanks!

Answer 1

You have closed the connection before reading lines:

import paramiko
client=paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
com="ls ~/desktop"
client.connect('MyIPAddress',MyPortNumber, username='username', password='password')
output=""
stdin, stdout, stderr = client.exec_command(com)

print "ssh succuessful. Closing connection"
stdout=stdout.readlines()
client.close()
print "Connection closed"

print stdout
print com
for line in stdout:
    output=output+line
if output!="":
    print output
else:
    print "There was no output for this command"

Answer 2

The code in the accepted answer may hang, if the command produces also an error output. See Paramiko ssh die/hang with big output.

An easy solution, if you do not mind merging stdout and stderr, is to combine them into one stream using Channel.set_combine_stderr:

stdin, stdout, stderr = client.exec_command(command)
stdout.channel.set_combine_stderr(True)
output = stdout.readlines()

---

If you need to read the outputs separately, see Run multiple commands in different SSH servers in parallel using Python Paramiko.

Answer 3

*Interactive example ： ====Part 1， this show the sh output in server ，at the end of is ">" need some input to continual or exit ======

selilsosx045:uecontrol-CXC_173_6456-R32A01 lteue$ ./uecontrol.sh -host localhost UE Control:Start UE control using: UE Control:java -Dlogdir= -Duecontrol.configdir=./etc -jar ./server/server-R32A01.jar -host localhost Loading properties from file /Users/lteue/Downloads/uecontrol-CXC_173_6456-R32A01/etc/uecontrol.properties Starting remote CLI towards host localhost Enter the command Q to exit the CLI, or the command HELP to get information on available commands. The CLI is ready for input. uec>

===========Pyhton code with peramiko ============*

Try below method ： while not stdout.channel.exit_status_ready():

def shCommand(server_list):
server_IP = server_list[0]
username  = server_list[1]
password  = server_list[2]

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(server_IP,22,username, password)strong text

commandList = ['list \n']
alldata = getUeInfo(ssh,commandList)
ssh.close()

def getUeInfo(ssh,commandList):
data_buffer = ""
num_of_input = 0
stdin, stdout, stderr = ssh.exec_command('cmd')
while not stdout.channel.exit_status_ready():
   solo_line = ""        

   if stdout.channel.recv_ready():

      solo_line = stdout.channel.recv(1024)  # Retrieve the first 1024 bytes
      data_buffer += solo_line               


   if(cmp(solo_line,'uec> ') ==0 ):    #len of solo should be 5 ,
     if num_of_input == 0 :
      data_buffer = ""    
      for cmd in commandList :
       #print cmd
       stdin.channel.send(cmd)
      num_of_input += 1
     if num_of_input == 1 :
      stdin.channel.send('q \n') 
      num_of_input += 1

return data_buffer 

Answer 4

As @jabaldonedo said you closed your SSHClient connection before reading the stdout. SSHClient can be used as a context manager. Using the SSHClient as a context manager helps prevent you from trying to access stdout and stderr after the ssh connection is closed. The resulting code in Python3 syntax looks like:

from paramiko import AutoAddPolicy, SSHClient

with SSHClient() as client:
    client.set_missing_host_key_policy(AutoAddPolicy)
    client.connect(
        'MyIPAddress',
        MyPortNumber, 
        username='username', 
        password='password'
    )

    com = "ls ~/desktop"
    stdin, stdout, stderr = client.exec_command(com)

    output = ''
    for line in stdout.readlines()
        output += line

if output:
    print(output)
else:
    print("There was no output for this command")