Consider the following scenario:


tail -f test.txt


nohup ./tail.sh &


nohup ./tail.sh > out.log &

Running both in a terminal has the same effect:

  • I regain control of the terminal after running ./tail.sh
  • No output from tail appears on the terminal

However, when running it using ssh (e.g. ssh <user>@<hostname> "<script>"):

  • invoke_explicitredirect.sh returns control to ssh (and terminates)
  • invoke.sh hangs until I send a SIGINT

man nohup states that nohup will automatically redirect output to 'nohup.out' if possible:

If standard output is a terminal, append output to 'nohup.out' if possible, '$HOME/nohup.out' otherwise.

What is the difference between letting nohup append to nohup.out and explicitly redirecting the output?


Standard output is not a terminal when you launch the command remotely through ssh. Use the -t option with ssh to get the same behavior with both of your commands.

More details on ssh and nohup: http://snailbook.com/faq/background-jobs.auto.html (taken from the wiki page: https://en.wikipedia.org/wiki/Nohup)

  • I'm not sure what happened. All I get is Connection to <host> closed, and no nohup.out file. If I add echo test > out2.log to both scripts, out2.log gets created, but still no nohup.out – neverendingqs Dec 30 '14 at 20:24
  • Just tried it with sleep (ssh <user>@<hostname> "<script>; sleep 1") and it worked. Looks like ssh was terminating too early. – neverendingqs Dec 30 '14 at 20:25
  • What is standard output when ssh is used? – neverendingqs Dec 30 '14 at 20:28
  • The remote command standard output is going to the ssh client input in both cases but when -t is used, it behaves like a terminal. Nohup has a different output handling depending on whether it is a terminal or not. – jlliagre Dec 30 '14 at 21:42
  • More details on ssh and nohup: snailbook.com/faq/background-jobs.auto.html (taken from the wiki page: en.wikipedia.org/wiki/Nohup). – neverendingqs Dec 31 '14 at 13:26

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