How do I prevent my .sh or .bat file from launching a second instance is I already have the file running?

Sir_Q1 · 02-18-2016, 01:01 AM

I am very new to the world of Linux, so please with as I describe my problem. I have .sh file that I'm using to launch a .jar file. My launching script in the file is:

java -Djava.net.preferIPv4Stack=true -Dsun.java2d.opengl=true -jar file-name.jar "/home/user/CIP_01/config/file-name.properties"

It works just fine and is quite reliable, however, if a user is not paying attention and minimizes the program (out of sight, out my thing) they can actually launch a second instance of the program. This causes a few problems for them.

My question is how can I prevent this from happening.

Thanks in advance.

grail · 02-18-2016, 01:40 AM

Have a look at the pgrep command. You can then look for your running program before launching.

Another alternative would be to store the PID at the start of the program in a temp file and then access it at the start to see if it exists and check that the PID is still running.

Sir_Q1 · 02-18-2016, 05:21 AM

Thanks for the quick reply. I'll go and check it out. Hopefully it's fairly intuitive.

BW-userx · 02-18-2016, 08:47 AM

add something like this in your script

Code:

#!/bin/bash

whatsrunning="$(pidof firefox)"

[[ $whatsrunning ]] && echo "$whatsrunning">/dev/null || echo " start applicating instead"

where firefox is your program you're checking to see if it
is already running. if yes then send results to NULL else start it.
OR

Code:

#!/bin/bash

whatsrunning="$(pidof firefox)"

[[ ! $whatsrunning ]] && echo "starting applicating"

if it is not running then start it, replace echo statement with the name of the app you want started to start it.

if it is already running then nothing will take place unless you code it to within your script.

Code:

#!/bin/bash


whatsrunning="$(pidof "whatever your program is called")"

[[ ! $whatsrunning ]] && java -Djava.net.preferIPv4Stack=true \
-Dsun.java2d.opengl=true \
-jar \
file-name.jar "/home/user/CIP_01/config/file-name.properties"

that might work, I don't know if I chopped it up properly in the right areas of that entire command.

Sir_Q1 · 02-18-2016, 03:00 PM

Cool thanks. It looks easy enough. I'll when I get back to the site.

Thank you very much

grail · 02-18-2016, 07:33 PM

The suggestion above is good, but be careful if you have more than one java application running as you cannot do pidof the other identifying pieces of the command.

BW-userx · 02-18-2016, 07:51 PM

good point @grail

I yanked this out of one of my other scripts. he maybe able to mod it. first he got a do, ps -au after he starts it for a test run then pick out all of the names of everything that whole command starts if it is in fact more then one app/proccess then write down all of the names of each peice that is running as a result of that whole command line. then ...

brain teaser for you @Sir_Q1

it is all here for you. All you got a do is figure out what to change and or add, or remove to make it work for you.... Learning is a proccess

Code:

if [ $(pgrep -u $USER setbg | wc -l) -ge 2 ] && [ $(pgrep -u $USER sleep | wc -l ) -ge 1 ]; then
	echo $(pgrep -u $USER setbg | wc -l) "pid# --" $(pgrep -u $USER sleep | wc -l)
	pkill -u $USER -o sleep #the program name is here
	pkill -u $USER -o setbg  #the script name is here
else

something else

fi