Wait until task is completed on Remote Machine through Python

Question

I am writing a program in python on Ubuntu. In that program I am trying to print a message after completing a task \"Delete a File\" on Remote machine (RaspberryPi), connect

Answer 1

In addition to doing what Sylvian Leroux suggests:

If your commands involve running a bash script that needs to keep running after paramiko closes the ssh session (every time you send a command this happens) use:

nohup ./my_bash_script.sh >/dev/null 2>&1.

nohup tells the system that this process should ignore the "hang up" signal received when the ssh session is closed.

>/dev/null 2>&1 redirects the output. This is necessary because in some situations control will not be given back to your python script until an output is received.

To run command line applications like "stress" and "vlc" and keep them running after you return, the only solution I have found is to put your commands in a bash script followed by a & or &>/dev/null than call that bash script with paramiko using the method I mention in the previous paragraph.

This seems a bit "hacky" but it is the only way I have found after days of searching.

Answer 2

This is indeed a duplicate of paramiko SSH exec_command(shell script) returns before completion, but the answer there is not terribly detailed. So...

As you noticed, exec_command is a non-blocking call. So you have to wait for completion of the remote command by using either:

• Channel.exit_status_ready if you want a non-blocking check of the command completion (i.e.: pooling)
• Channel.recv_exit_status if you want to block until the command completion (and get back the exit status — an exit status of 0 means normal completion).

In your particular case, you need the later:

stdin, stdout, stderr = client.exec_command(filedelete)  # Non-blocking call
exit_status = stdout.channel.recv_exit_status()          # Blocking call
if exit_status == 0:
    print ("File Deleted")
else:
    print("Error", exit_status)
client.close()