Here is my general question: How do you log into a remote server, kick off a continuously running process, redirect the standard output of that process to a file on the local machine, and have all of this run in the background (on the local machine)?
More specifically, I'm trying to pipe tshark output from a remote Raspberry Pi to my local machine (actually another remote machine with Windows running Cygwin - long story) and write it to a log file. I started out by running the command without output redirection:
ssh pi@remotehost "\
sudo tshark \
-i wlan1mon \
-I -l -f broadcast \
-Y wlan.fc.subtype==4 \
-T fields \
-e wlan.sa \
-e frame.time_epoch"
This seems to working as I would expect it to; I get a stream of data in the terminal. Next I tried to add output redirection:
ssh pi@remotehost "\
sudo tshark \
-i wlan1mon \
-I -l -f broadcast \
-Y wlan.fc.subtype==4 \
-T fields \
-e wlan.sa \
-e frame.time_epoch" \
> /var/tshark.out
This also seems to work as expected; I see standard error written to the terminal and after I terminate the process and check the output file (/var/tshark.out) I see the standard output from tshark. Next I try to run this in the background on my machine:
ssh pi@remotehost "\
sudo tshark \
-i wlan1mon \
-I -l -f broadcast \
-Y wlan.fc.subtype==4 \
-T fields \
-e wlan.sa \
-e frame.time_epoch" \
> /var/tshark.out &
Unfortunately this doesn't have the desired effect. When I check the output file it's empty, and when I check the job status (by running the "jobs" command) I see that it's stopped. Here is the output from jobs (I've reformatted it slightly for readability):
[1]+ Stopped ssh pi@remotehost
"sudo tshark
-i wlan1mon
-I -l -f broadcast
-Y wlan.fc.subtype==4
-T fields
-e wlan.sa
-e frame.time_epoch"
> /var/tshark.out &
This led me down the path of trying various permutations of background-ing and nohup-ing both the remote and local process, but to no avail.
