Discussion between r3wt and KasiyA

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16:22

0

Q: bash comparison of integer always returns true?

I have the following simple bash script. for some reason it always returns true. #!/bin/bash service=hhvm status=($(ps -ef | grep -v grep | grep $service | wc -l)) if [[ $status -eq 0 ]]; then echo "starting $service" service hhvm start else echo "$service running" fi

KasiyA

just remove spaces around =. change foo = 3 --> foo=3 and run your script with bash /path/to/script

r3wt

the real var is status=$(ps -ef | grep -v grep | grep $service | wc -l)

@ThomasW. unfortunately, i have been banned.

@ThomasW. no the first question i asked got a ton of down votes, so my account is more or less teetering on the edge. every down vote my account becomes banned. every couple hundred points it gets unbanned. its stupid.

KasiyA

remove outer parentheses from status=($(ps -ef | grep -v grep | grep $service | wc -l))

r3wt

@KasiyA already tried it. out put of the call is 3 if service running, 0 if stopped, but always says that its running.

KasiyA

How do you run the script? with sh /path/to or bash /path/to? and what "out of call" is there? and what does mean grep -v grep there?

r3wt

16:22

i run it with ./script.sh

KasiyA

@P.-H.Lin I know that, but according to what pattern? "grep" is patten there?

r3wt

KasiyA, again that's not the problem. the call returns 3, which it is supposed to. even after updating as you suggested, the script still doesn't work as expected.i appreciate your attempts, but no need to try any further. it is my problem i'll try to figure it out eventually.

KasiyA

@r3wt Which call? I'm stuck on it. the status=($(ps -ef | grep -v grep | grep $service | wc -l)) line is completely invalid if you want to save the integer number in it.

r3wt

@KasiyA the line you just asked me to change. the output returns 3 if the service is running, 0 if not.

KasiyA

Run alone service=hhvm; ps -ef | grep -v grep | grep $service | wc -l in terminal and now what do you see? 3 , 4 ,0 ? what? please reply.

r3wt

16:22

@KasiyA 1 is what i see.

KasiyA

And when service=hhvm; ps -ef | grep $service | wc -l

r3wt

2 27 248 - after that command

KasiyA

Ok. last question: please post the results of service=hhvm; ps -ef | grep -v grep | grep $service | wc -l when hhvm service is running and when it's not running

r3wt

@KasiyA 1 when running, 0 when not. please bear in mind, there may be more than 1 running at any given time, so long as atleast 1 is running the check should pass.

KasiyA

This is silly question but what is the output of if [[ 3 == 0 ]]; then echo "true" ; fi and if [[ 3 -eq 0 ]]; then echo "true" ; fi

r3wt

16:22

KasiyA, hi

KasiyA

Hi

r3wt

There was no output for either one as should be. which is why i was so perplexed to begin with. the script should work or so i thought

KasiyA

try

#!/bin/bash
service=hhvm
status=$(ps -ef | grep -v "grep"| grep "$service" | wc -l)
if [[ $status -eq 0 ]]; then
echo "starting $service"
service hhvm start
else
echo "$service is running"
fi

r3wt

it's crazy man

i'm on ubuntu 14.04 fwiw

KasiyA

So you always get false not true

do you know where the problem is?

r3wt

16:32

no, i don't. i don't even know bash really. just found this when googling and hacked on it but never could get it working

KasiyA

1: when the service isn't running it does not returns ZERO

r3wt

null?

damn

you were trying to let me figure that out on my own huh

KasiyA

run:
service hhvm stop;service=hhvm; ps -ef | grep -v grep | grep $service | wc -l
then:

service hhvm start;service=hhvm; ps -ef | grep -v grep | grep $service | wc -l

and post please please actual result

r3wt

0

1

KasiyA

#!/bin/bash
service=hhvm
status=$(ps -ef | grep -v "grep"| grep "$service" | wc -l)
if [[ $status == 0 ]]; then
echo "starting $service"
service hhvm start
else
echo "$service is running"
fi

r3wt

16:44

nope, still no good

KasiyA

and

#!/bin/bash
if ! (($(ps -ef | grep -v "grep"| grep "hhvm" | wc -l))) ; then
echo "starting hhvm"
service hhvm start
else
echo "hhvm is running"
fi

r3wt

it works man

KasiyA

Cool

r3wt

nice job

KasiyA

I'll post it as answer and please mark it as accept :)

r3wt

16:48

quick question, i can run this as a cron job and dump output to dev null right?

aka the bitbucket

KasiyA

And before that. please test this
#!/bin/bash
service=hhvm
if ! (($(ps -ef | grep -v "grep"| grep "$service" | wc -l))) ; then
echo "starting $service"
service hhvm start
else
echo "$service is running"
fi

and reply any changes

r3wt

yep, it worked man

good job sir, i truly thank you for your help!

KasiyA

ok I will post it as answer, please wait and check.

r3wt

if you post answer i will upvote and accept

KasiyA

:)

r3wt

16:51

for your hard work. man you really helped me out alot

i am really greatful. ironically, i tried quoting $service everywhere but inside of the variable assignment

KasiyA

I have posted my answer

@r3wt are you here?

You asked me about cron?

At what times do you want to run it as cron?

1. Saving the script (example `script.sh`)
2. Make it executable `chmod +x /path/to/script.sh`
3. open the `crontab` file by `VISUAL=gedit crontab -e` or `EDITOR=gedit crontab -e`

4. Now copy and paste '* * * * * /path/to/script.sh' (without quotes) at end of it and save the file.
This will run your command/script every minute

If you want run it in different times, the cron syntax is as following

.---------------- minute (0 - 59)
| .------------- hour (0 - 23)
| | .---------- day of month (1 - 31)

Good luck.

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Discussion between r3wt and KasiyA