How to Execute multiple command using nohup

Question

I need to execute multiple commands using nohup. Each command should be executed after the previous command.

I used this command as an example:

nohup wget $url && wget $url2 > /dev/null 2>&1 &

However that command did not work.

What command should I use for this purpose?

A more complicated example: `nohup sh -c 'echo $SU_PASSWORD | /afs/cs/software/bin/reauth; python -u ~/diversity-for-predictive-success-of-meta-learning/div_src/diversity_src/experiment_mains/main_sl_with_ddp.py --manual_loads_name sl_hdb1_5cnn_adam_cl_filter_size --filter_size 4 > $OUT_FILE 2> $ERR_FILE' > nohup.out$SLURM_JOBID &` — Charlie Parker, Nov 15 '22 at 18:43

jw013 · Accepted Answer · 2014-05-14T17:02:52.013

96

Wrap it in sh -c:

nohup sh -c 'wget "$0" && wget "$1"' "$url1" "$url2" > /dev/null &

edited May 14 '14 at 17:02

answered Sep 05 '12 at 14:06

jw013

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when I launch nohup I get "nohup: ignoring input and redirecting stderr to stdout" so isn't the "2>&1" redundant? – harschware May 14 '14 at 16:38
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Probably. I think when I wrote the answer I just copied it from the question. – jw013 May 14 '14 at 17:02
do you the the `&` at the end of a `nohup`? – Charlie Parker Nov 14 '22 at 22:46

score 12 · Answer 2 · answered Mar 13 '13 at 08:47

12

Wouldn't it be far simpler to create your list of commands in a separate shell file, e.g. command.sh, without any nohup.

Then you call:

nohup bash command.sh

answered Mar 13 '13 at 08:47

assaf

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For some reason this isn't working for me. When I press enter after running nohup, it exits and does not keep running the script in the background – karlpy Jan 13 '22 at 23:00
It doesn't work on the background. – postgresnewbie Jun 10 '22 at 08:58
do you the the `&` at the end of a `nohup`? – Charlie Parker Nov 14 '22 at 22:46

janos · Answer 3 · 2012-09-06T07:39:16.107

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Others have already answered about nohup. As a practical side note: I recommend doing this kind of thing within a screen or tmux session. That way you can disconnect, then reconnect later and see the output and final result.

edited Sep 06 '12 at 07:39

answered Sep 05 '12 at 15:38

janos

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This answer is great for interactive scenarios, but doesn't make sense for scripts or automation. – Jonathan Hartley Jun 13 '16 at 18:09

score 4 · Answer 4 · answered Sep 05 '12 at 15:11

4

It would be simpler like this:

nohup sh -c "wget $url && wget $url2" > /dev/null 2>&1 &

This however may cause issues if the URLs contain special characters so for a safer option you can use:

nohup sh -c "wget \"$url\" && wget \"$url2\"" > /dev/null 2>&1 &

answered Sep 05 '12 at 15:11

Didi Kohen

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The only safe way to pass parameters to `sh -c` is via separate arguments, which can be accessed via the positional parameters (`$0`, `$1`, ...). There is no easy or simple way to quote arguments properly for string parsing. Your attempt to use escaped double quotes fails if `$url` itself contains double quotes. Try `a='problem"'; sh -c "echo \"$a\""` yourself and see - you should get a syntax error because `sh -c` tries to run `echo "problem""`. – jw013 Sep 05 '12 at 15:57
@jw013 Out of interest, does your objection apply equally to the accepted answer by -oh. By you. Presumably not, then. But I don't understand why not! :-) – Jonathan Hartley Jun 13 '16 at 18:12
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@JonathanHartley I'm not sure I understand your question. If you compare this answer to mine carefully you should notice a difference in the way `$url` and `$url2` are used. – jw013 Jun 13 '16 at 22:50
@jw013 Ah, of course. I was being silly. Thank you for setting me straight. – Jonathan Hartley Jun 14 '16 at 16:40

score 0 · Answer 5 · answered Jul 30 '21 at 22:52

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One alternative is to create an additional file with the sequential part of the script and call it with nohup. Although, if you're passing parameters, that's going to add a little bit extra work.

answered Jul 30 '21 at 22:52

Íhor Mé

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score 0 · Answer 6 · answered Nov 15 '22 at 18:42

A more complicated example:

nohup sh -c 'echo $SU_PASSWORD | /afs/cs/software/bin/reauth; python -u ~/diversity-for-predictive-success-of-meta-learning/div_src/diversity_src/experiment_mains/main_sl_with_ddp.py --manual_loads_name sl_hdb1_5cnn_adam_cl_filter_size --filter_size 4 > $OUT_FILE 2> $ERR_FILE' > nohup.out$SLURM_JOBID &

score -2 · Answer 7 · answered Jan 07 '21 at 23:30

-2

might be helpful for someone:

nohup $(wget $url && wget $url2) &

answered Jan 07 '21 at 23:30

Nurik

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Welcome to the site. Would you explain the purpose of the command substitution? In its current form, your solution would try to execute the output generated by the two `wget` calls in a `nohup` environment. – AdminBee Jan 08 '21 at 08:37
Thanks @AdminBee :) Correct, both wget will output to hohup and for nohup it is like one single command – Nurik Jan 09 '21 at 11:46

How to Execute multiple command using nohup

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