Hey all,
I wrote a very basic script to determine if cassandra db is running. I'm setting a variable called 'pid' to the output of a ps | grep like to grab the pid of the cassandra process.
#!/bin/bash pid=$(ps -ef | grep cassandra | grep -v grep | grep -i -v -e grep -e screen -e s3fs|awk '{print $2}')
if [[ -e $pid ]] then echo "Cassandra is running with pid: $pid" else echo "Cassandra is DOWN!!!" fi
But for some reason the script doesn't realize that the pid variable has been set, and fails the condition. It then reports that Cassnadra is DOWN!!!".
[root@web1:~] #sh -x ./bin/check-cass.sh ++ ps -ef ++ grep -v grep ++ grep -i -v -e grep -e screen -e s3fs ++ awk '{print $2}' ++ grep cassandra + pid=26979 + [[ -e 26979 ]] + echo 'Cassandra is DOWN!!!' Cassandra is DOWN!!!
Can anybody tell me where I'm going wrong here? Because from what I can see, clearly the pid variable is being set so the script should be reporting that cassandra is up!
I'd appreciate any advice you may have.
Thanks, Tim
Tim Dunphy bluethundr@gmail.com a écrit :
Hey all,
Hi,
-e checks file existence. As you don’t have a file named 26979 in your pwd, test fails logically. If you want to know if variable is set, you can use -z $pid. You could also try -d /proc/$pid.
HTH, Laurent.
On Sun, 2015-04-19 at 13:15 -0400, Tim Dunphy wrote:
Hey all,
I wrote a very basic script to determine if cassandra db is running. I'm setting a variable called 'pid' to the output of a ps | grep like to grab the pid of the cassandra process.
Insert an extra line after #!/bin/bash
set -xv
which will show helpful debug messages.
"-e" means "if file exists". You should use "-n"
That did it!!
[root@web1:~] #./bin/check-cass.sh Cassandra is running with pid: 26979
This is what the script looks like now:
#!/bin/bash pid=$(ps -ef | grep cassandra | grep -v grep | grep -i -v -e grep -e screen -e s3fs|awk '{print $2}')
if [[ -n $pid ]] then echo "Cassandra is running with pid: $pid" else echo "Cassandra is DOWN!!!" fi
Insert an extra line after #!/bin/bash
set -xv which will show helpful debug messages.
Good tip! But I ran the script with sh +x . I guess that running it with sh +xv would do the same thing. But that is a useful tip to include the debug lines right in the script. I'll have to remember that for next time!
Thanks! :)
Tim
On Sun, Apr 19, 2015 at 1:55 PM, Always Learning centos@u64.u22.net wrote:
On Sun, 2015-04-19 at 13:15 -0400, Tim Dunphy wrote:
Hey all,
I wrote a very basic script to determine if cassandra db is running. I'm setting a variable called 'pid' to the output of a ps | grep like to grab the pid of the cassandra process.
Insert an extra line after #!/bin/bash
set -xv
which will show helpful debug messages.
-- Regards,
Paul. England, EU. Je suis Charlie.
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On Sun, Apr 19, 2015 at 09:40:29PM -0400, Tim Dunphy wrote:
Good tip! But I ran the script with sh +x . I guess that running it with sh
You should use "bash -x" ("bash" and not "sh" because sh may not be bash everywhere; eg Ubuntu; "-x" and not "+x" because "-x" means "turn on debug" but "+x" means "turn _off_ debug")
Once upon a time, Stephen Harris lists@spuddy.org said:
On Sun, Apr 19, 2015 at 09:40:29PM -0400, Tim Dunphy wrote:
Good tip! But I ran the script with sh +x . I guess that running it with sh
You should use "bash -x" ("bash" and not "sh" because sh may not be bash everywhere; eg Ubuntu; "-x" and not "+x" because "-x" means "turn on debug" but "+x" means "turn _off_ debug")
Unless you have specific bashisms (which I don't think the original did, and you should mostly avoid in scripts), sh -x will be fine.
On Sun, Apr 19, 2015 at 09:00:06PM -0500, Chris Adams wrote:
Once upon a time, Stephen Harris lists@spuddy.org said:
You should use "bash -x" ("bash" and not "sh" because sh may not be bash everywhere; eg Ubuntu; "-x" and not "+x" because "-x" means "turn on debug" but "+x" means "turn _off_ debug")
Unless you have specific bashisms (which I don't think the original did, and you should mostly avoid in scripts), sh -x will be fine.
It's a matter of "consistency". The script began #!/bin/bash and so a direct shell invocation should _also_ use the same command.
It's a matter of "consistency". The script began #!/bin/bash and so a direct shell invocation should _also_ use the same command.
Good point. I'll try to keep that in mind.
Thank you, Tim
On Sun, Apr 19, 2015 at 10:04 PM, Stephen Harris lists@spuddy.org wrote:
On Sun, Apr 19, 2015 at 09:00:06PM -0500, Chris Adams wrote:
Once upon a time, Stephen Harris lists@spuddy.org said:
You should use "bash -x" ("bash" and not "sh" because sh may not be
bash
everywhere; eg Ubuntu; "-x" and not "+x" because "-x" means "turn on
debug"
but "+x" means "turn _off_ debug")
Unless you have specific bashisms (which I don't think the original did, and you should mostly avoid in scripts), sh -x will be fine.
It's a matter of "consistency". The script began #!/bin/bash and so a direct shell invocation should _also_ use the same command.
--
rgds Stephen _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Once upon a time, Tim Dunphy bluethundr@gmail.com said:
pid=$(ps -ef | grep cassandra | grep -v grep | grep -i -v -e grep -e screen -e s3fs|awk '{print $2}')
You can probably replace that with a much cleaner pid=$(pidof cassandra).
You can probably replace that with a much cleaner pid=$(pidof cassandra).
Good to know! I hadn't heard of pidof before. However this is what I get when I run it:
[root@web1:~] #pidof cassandra [root@web1:~] #
Returns nothing. However:
[root@web1:~] #pidof java 27210 11418 10852
Gives me a few pids. Only one of which belongs to cassandra, as I have a few java processes running.
I still find that my little script isolates exactly the pid of cassandra that I would need to shutdown.
[root@web1:~] #check-cass.sh Cassandra is running with pid: 27210
I really need to turn this into an init script. Which I probably will. But this is just for a hobby project ,and I'm a little too lazy to do it this weekend. Maybe next weekend.
Thanks, Tim
On Sun, Apr 19, 2015 at 9:58 PM, Chris Adams linux@cmadams.net wrote:
Once upon a time, Tim Dunphy bluethundr@gmail.com said:
pid=$(ps -ef | grep cassandra | grep -v grep | grep -i -v -e grep -e
screen
-e s3fs|awk '{print $2}')
You can probably replace that with a much cleaner pid=$(pidof cassandra).
-- Chris Adams linux@cmadams.net _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Once upon a time, Tim Dunphy bluethundr@gmail.com said:
Good to know! I hadn't heard of pidof before. However this is what I get when I run it:
Try pid=$(pidof -x cassandra). Normal pidof calls look for programs with the given name, but scripts/interpreted programs show up with the interpreter first and then the program name. The -x options tells it to look for script-like things as well.
-
Always Learning -
Chris Adams -
Laurent Wandrebeck -
Stephen Harris -
Tim Dunphy