Unable to run commands in sequence.

[mukkid]

Hello! I am trying to run commands against a Cisco network device in series using something like this

with asyncssh.connect(MY_HOST) as conn:
    cmds = ['show version', 'show arp']
    for cmd in cmds:
        out = await conn.run(cmd)
        print(out.stdout)

But when I run it, the channel seems to be closed after the first command finishes.

'Proper version info here........'

ChannelOpenError('')

Am I missing something painfully obvious or do you think it's something to do with the network device? For what it's worth, I don't see this issue when using paramiko though that doesn't get me the async capabilities. Curiously, I can get it to work using scrapli using asyncssh as the backend, but I'd rather use this library standalone. Any input is appreciated. Thank you!

[ronf]

Not all SSH implementations support opening multiple sessions/channels on a single connection. Some of them will close the connection as soon as the first (and only) session exits, and that's what is probably happening here. The conn.run() call opens a new "exec" session on conn designed to run a single command and collect up all the output from that command. After that, the session is closed.

Your only real options here are to either open a separate connection for each command, or to open a "shell" session, where you don't provide a command as an argument and instead read and write data on stdin/stdout/stderr to read any initial banner and shell prompt sent on the connection, write a command to execute, and then read the output of the command and the prompt which indicates when the command output is complete. Unfortunately, this can be a bit tricky, especially in terms of figuring out a safe prompt to use.

There are multiple examples if you search through past GitHub issues where people ask about this. Look for uses of readuntil().