I need to create a SSH BASH script (on Debian linux) to test if 'java' process is running.
Here how it should look like:
IF 'java' process is not running THEN run ./start.sh
to test if java process is running, I can make this test:
ps -A | grep java
This script should run every minute (I guess in a CRON)
Regards
First of all, to run a job every minute in cron, your crontab should look like this:
* * * * * /path/to/script.sh
Next, you have a few different options for detecting a Java process.
Note that each of the following is a negation: they detect the absence of Java:
With pgrep:
if [ ! $(pgrep java) ] ; then
# no java running
fi
With pidof:
if [ ! $(pidof java) ] ; then
# no java running
fi
With ps and grep:
if [ ! $(ps -A | grep 'java') ] ; then
# no java running
fi
Of these, pgrep and pidofare probably the most efficient. Don't quote me on that, though.
The check you are doing with PS and GREP doesn't look very detailed. What if other Java processes are running ? You may detect those, and come to a wrong conclusion, because you are just checking "any" Java, not some specific Java.
With pidof would be something like this:
script.sh
pidof java;
if[$? -ne 0];
then
# here put your code when errorcode of `pidof` wasn't 0, means that it didn't find process
# for example: /home/user/start.sh
# (please don't forget to use full paths if you want to use it in cron)
fi
Especially for haters:
man pidof:
EXIT STATUS
0 At least one program was found with the requested name. 1 No program was found with the requested name.
