CkPython

Release an SSH Channel's Local Resources

Demonstrates the Chilkat Ssh.ChannelRelease method, which releases Chilkat's retained local resources for a channel after all output and exit information has been retrieved. The only argument is the channel number.

Background: Chilkat retains a channel's buffered output and exit information after the channel closes, so you can still read a command's final output. That retention costs memory, and a long-running program that opens many channels should release each one when finished with it. Note this is not a channel-closing method — it sends neither EOF nor CLOSE. Retrieve everything you need first, because releasing discards it.

Chilkat CkPython Downloads

Download Chilkat for CkPython

CkPython

import sys
import chilkat

success = False

#  Demonstrates the Ssh.ChannelRelease method, which releases Chilkat's retained local resources
#  for a channel after all output and exit information has been retrieved.  The only argument is
#  the channel number.

ssh = chilkat.CkSsh()

sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  Normally you would not hard-code the password in source.  You should instead obtain it
#  from an interactive prompt, environment variable, or a secrets vault.
password = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin",password)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  Open a session channel.  A negative return value indicates failure.
channelNum = ssh.OpenSessionChannel()
if (channelNum < 0):
    print(ssh.lastErrorText())
    sys.exit()

success = ssh.SendReqExec(channelNum,"uname -a")
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
#  it, this call waits forever if the server never sends channel close.
ssh.put_ReadTimeoutMs(15000)

#  Retrieve everything of interest before releasing the channel.
success = ssh.ChannelReceiveToClose(channelNum)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

output = ssh.getReceivedText(channelNum,"utf-8")
if (ssh.get_LastMethodSuccess() == False):
    print(ssh.lastErrorText())
    sys.exit()

print(output)

#  Release the retained local resources.  This does not send EOF or CLOSE.
ssh.ChannelRelease(channelNum)

ssh.Disconnect()