Tue 24 February 2015

Filed under programming

Tags tmux

I tend to run the same SNMP probes on multiple devices quite often. The devices are always the same, the OIDs change. To simplify this I created a small Python script running the commands in a tmux session.

However, there seems to be a small bug/annoyance in tmux which makes it nearly impossible to run a command with special characters in it's parameters directly via tmux. Instead, "injecting" the keystrokes into the running session works fine.

I started off writing this in bash, but due to the issue mentioned above, I ended up writing it in Pythong, making the code a lot cleaner. Albeit unnecessary:

Run "snmpwalk" on multiple devices simultaneously in separate tmux tabs.

from collections import namedtuple
from os import environ
from subprocess import check_call as run
import sys

environ['TERM'] = 'xterm-256color'  # Hint for tmux to enable 256 colours.

Connection = namedtuple('Connection', 'ip, community, name')

TMUX_NAME = 'snmpt-probe'
    Connection('', 'helloworld', 'Device 1'),
    Connection('', 'helloworld', 'Device 2'),
    Connection('', 'helloworld', 'Device 3'),
    Connection('', 'helloworld', 'Device 4'),

def exec_(ip, oid, community):
    Run a command using ``tmux send-keys``.

    This is a workaround. Executing the command directly does not work if a
    parameter contains special characters.
    run(['tmux', 'send', '-t', TMUX_NAME, ' snmpwalk -v2c -c "'])
    run(['tmux', 'send', '-t', TMUX_NAME, community])
    run(['tmux', 'send', '-t', TMUX_NAME, '" %s %s | less' % (ip, oid)])
    run(['tmux', 'send', '-t', TMUX_NAME, 'ENTER'])

def main():

    # Ask the user to enter the OID
    oid = input('OID: ').strip()
    if not oid:
        print('OID cannot be empty!', file=sys.stderr)
        return 1

    # Create a new, empty tmux session
    run(['tmux', 'new', '-s', TMUX_NAME, '-d'])

    # give the first window it's proper name
    run(['tmux', 'rename-window', '-t', '0', TARGET_DEVICES[0].name])

    # create the remaining tabs with appropriate names
    for _, _, name in TARGET_DEVICES[1:]:
        run(['tmux', 'new-window', '-n', name])

    # run the snmpwalk commands
    for ip, community, name in TARGET_DEVICES:
        run(['tmux', 'select-window', '-t', name])
        exec_(ip, oid, community)

    # Attach the tmux session
    run(['tmux', 'attach', '-t', TMUX_NAME])
    return 0

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