Run a shell script and immediately background it, however keep the ability to inspect its output

Question

How can I run a shell script and immediately background it, however keep the ability to inspect its output any time by tailing /tmp/output.txt.

It would be nice if I can foreground the process too later.

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P.S.

It would be really cool if you can also show me how to "send" the backgrounded process in to a GNU screen that may or may not have been initialized.

Answer 1

To 'background' a process when you start it

Simply add an ampersand (&) after the command.

If the program writes to standard out, it will still write to your console / terminal.

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To foreground the process

Simply use the fg command. You can see a list of jobs in the background with jobs.

For example:

sh -c 'sleep 3 && echo I just woke up' & jobs

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To background a currently running process

If you have already started the process in the foreground, but you want to move it to the background, you can do the following:

1. Press Ctrl+z to put the current process to sleep and return to your shell. This process will be paused until you send it another signal.
2. Run the bg command to resume the process, but have it run in the background instead of the foreground.

Answer 2

I tried nohup but my process was getting stopped after a day or two , so i tried this simple bash script to rerun my command after it stops

run.sh

while true; do
[ -e stopme ] && break
python3 main.py # your command here
done

then do

nohup bash run.sh &

Answer 3

One easy to use approach that allows managing multiple processes and has a nice terminal UI is hapless utility.

Install with pip install hapless (or python3 -m pip install hapless) and just run

$ hap run my-command  # e.g. hap run python my_long_running_script.py
$ hap status  # check all the launched processes
$ hap logs 4  # output logs for you 4th background process
$ hap logs -f 2  # continuously stream logs for the 2nd process

See docs for more info.

Answer 4

Another way is using the nohup command with & at the end of the line.

Something like this

nohup whatevercommandyouwant whateverparameters &

This will run it in the background and send its output to a nohup.log file.