I am writing a script in Python for login to ssh and read the output of commands just executed. I am using paramiko package for this. I am trying to execute command "top" and get its output printed on the console. However, I am not able to do this. Please find the snippet:
import sys
import time
import select
import paramiko
host = 'localhost'
i = 1
#
# Try to connect to the host.
# Retry a few times if it fails.
#
while True:
print 'Trying to connect to %s (%i/30)' % (host, i)
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, port=22, username='dummy', password='dummy')
print "Connected to %s" % host
break
except paramiko.AuthenticationException:
print "Authentication failed when connecting to %s" % host
sys.exit(1)
except:
print "Could not SSH to %s, waiting for it to start" % host
i += 1
time.sleep(2)
# If we could not connect within time limit
if i == 30:
print "Could not connect to %s. Giving up" % host
sys.exit(1)
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("uname")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print '-------------------------------'
print stdout.channel.recv(1024)
print '-------------------------------'
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("top -n 1")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print '-------------------------------'
print stdout.channel.recv(1024)
print '-------------------------------'
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("uname")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print '-------------------------------'
print stdout.channel.recv(1024)
print '-------------------------------'
#
# Disconnect from the host
#
print "Command done, closing SSH connection"
ssh.close()
Output: Trying to connect to localhost (1/30)
Linux
Linux
Command done, closing SSH connection
I am not sure, where I am doing wrong. I am able to get output of other linux commands though. But not sure, why top command's output is not getting printed.
as Jason S pointed out
stdin, stdout, stderr = ssh.exec_command("top -b -n1")
print stdout.read()
works just fine.
top
normally uses curses for display rather than just printing. Try the -b
for batch option along with the -n 1
you have (top options vary by platform, check the manpage). And in the future, try isolating the problem more - if you were to invoke top
via ssh
on the command line without your script you would still have an issue.
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