CkPython

Send Text on an SSH Channel

Demonstrates the Chilkat Ssh.ChannelSendString method, which encodes text using a charset and sends the resulting bytes on a channel. The arguments are the channel number, the text, and the charset. No line ending or terminator is added automatically.

Background: This is how you type into a remote shell programmatically. The most common mistake is forgetting the newline — the remote shell will not act on a command until it receives one, so the terminator must be part of the text you send. An empty string is valid and sends zero bytes. The charset governs how the text becomes bytes on the wire.

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import sys
import chilkat

success = False

#  Demonstrates the Ssh.ChannelSendString method, which encodes text with a charset and sends
#  the bytes on a channel.  The 1st argument is the channel number, the 2nd is the text, and the
#  3rd is the charset.  No line ending is added automatically.

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()

channelNum = ssh.OpenSessionChannel()
if (channelNum < 0):
    print(ssh.lastErrorText())
    sys.exit()

#  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
#  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
#  echo typed commands back, and skips interactive login scripts.  The output is therefore
#  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
#  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
success = ssh.SendReqShell(channelNum)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  Send a command.  The trailing newline must be included because no terminator is added.
success = ssh.ChannelSendString(channelNum,"ls -l /tmp\n","utf-8")
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  Read the shell's response.
pollTimeoutMs = 2000
result = ssh.ChannelReadAndPoll(channelNum,pollTimeoutMs)
if (result == -1):
    print(ssh.lastErrorText())
    sys.exit()

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

print(output)

ssh.Disconnect()