When GNU parallel exit,my program also fail

Question

I am using GNU parallel to run a bash function. The function just contains the bash script to restart my program. At first, the restart is ok, but when parallel exits, my program also fails. Why?

#!/bin/bash
function_A () {
 local module=1ドル
 set -x
 cd /dir/${module}/;sh stop_${module}.sh;sh start_${module}.sh;sleep 10
}
export -f function_A
parallel --tag --onall --env function_A -S my_host function_A ::: my_program

Output from ps:

root 12967 0.0 0.0 65960 1152 pts/1 Ss+ 16:30 0:00 bash -c echo $SHELL | egrep "/t?csh" > /dev/null && echo CSH/TCSH DO NOT SUPPORT newlines IN VARIABLES/FUNCTIONS && exec false;? eval `echo $SHELL | grep "/t\{0,1\}csh" > /dev/null && echo setenv PARALLEL_SEQ 1\; setenv PARALLEL_PID 6431 || echo PARALLEL_SEQ=1\;export PARALLEL_SEQ\; PARALLEL_PID=6431\;export PARALLEL_PID` ; tty >/dev/null && stty isig -onlcr -echo;echo $SHELL | grep "/t\{0,1\}csh" > /dev/null && setenv function_A \(\)\ \{\ \ local\ module=\1ドル\;"?"\ set\ -x\;"?"\ cd\ /dir/\$\{module\}/\;"?"\ sh\ test.sh\;"?"\ sleep\ 10"?"\} || export function_A=\(\)\ \{\ \ local\ module=\1ドル\;"?"\ set\ -x\;"?"\ cd\ /dir/\$\{module\}/\;"?"\ sh\ test.sh\;"?"\ sleep\ 10"?"\} && eval function_A"$function_A";function_A my_program

• user78605: Not passing any args to function so 1ドル will be empty. Also post the error in the question
• slowlaris: But my_program is 1ドル.when parallel running,my_program start ok.when parallel stop,my_program also fail,why?
• konsolebox: What do you mean the program also fails? Any error message you could share?
• slowlaris: My program has already received requests during sleep 10. But after sleep 10 ,then parallel exit,I can not find my_program in ps commond.
• Barmar: The script to restart your program needs to run it in a new session. The same thing will happen if you start it from a normal shell and then logout.

Answer 1

As I understand your problem, you want to start a daemon on the remote machine, and when GNU Parallel exits, the daemon should continue running.

For that you should use a tool that allows a command to continue even after you logout. I know of 3 such tools:

nohup
screen
tmux

So use these in your function:

 cd /dir/${module}/;nohup sh stop_${module}.sh;nohup sh start_${module}.sh;sleep 10

Answer 2

Try nohup sh "start_${module}.sh" &:

#!/bin/bash
function_A () {
 local module=1ドル
 set -x
 cd "/dir/${module}/"
 sh "stop_${module}.sh"
 nohup sh "start_${module}.sh" &
 sleep 10
}
export -f function_A
parallel --tag --onall --env function_A -S my_host function_A ::: my_program

The nohup command will cause the underlying script to not exit when the shell exits, for example, during a logout. '&' will immediately background the process. Also, make sure your "start_${module}.sh" works non-interactively; for example, try running it as sh -c 'sh start_${module}.sh') to make sure it works.