how to enable some commands during run time in a shell script - linux

Question

I have written 1 shell script to run Jstack command for a particular Process ID (PID).
But some time it may happen that multiple PIDs are there in a server for Java process.
At that case i want to run that many Jstack commands giving respective PIDs as input to the command.
Eg. If one application has 2 servers (1 tomcat and 1 jboss), then I need to run 2 JStack commands to capture 2 different logs for 2 processes.
So how to handle or check so that the script will automatically decide how many PIDs r there for java process and will run the commands written inside the script?
My script is getting all the PIDs active by
PID1=$(ps -ef|grep java|grep jboss| awk '{print $2}' )
and
PID2=$(ps -ef|grep java|grep tomcat| awk '{print $2}' )
after that I am running Jstack commands as
jstack $PID1 > jStack1.txt & and jstack $PID2 > jStack2.txt &

Answer 1

To get the pid you can just use pgrep instead of ps/grep/grep/awk:
for pid in $(pgrep -f "tomcat|jboss")
do
jstack $pid >> jStack1.txt
done

Answer 2

you need to combine the pids into one list and loop round them.
So something like this to get a seperate file for each pid:
for pid in $( ps -ef | egrep "tomcat|jboss" | awk '{print $2}')
do
jstack $pid > jstack.$pid.txt
done
Following on from your last comment
I'm not sure what you are trying to do with the array and multiple jstack calls in the loop as it will iterate once for each pid, not give you two pids in the loop, and the $0 & $1 indices don't make sense (did you mean just 0 & 1?), and you are using $N each time but the increment for it is commented out so will stay as 0.
If you are sure there can only be two pids, one for tomcat and one for jboss, then your inital code with sleeps added would do it:
#!/bin/bash
Sleep1=$1
# sleep for the first requested time
sleep $Sleep1
# do the tomcat jstack
PID1=$(ps -ef | grep java| grep tomcat | awk '{print $2}')
jstack $PID1 > jstack.tomcat.$PID1.txt
# sleep for another 60secs
sleep 60
# do the jboss jstack
PID2=$(ps -ef | grep java| egrep "jboss|JBoss" | awk '{print $2}')
jstack $PID2 > jstack.jboss.$PID1.txt
If there can be multiple tomcat processes and multiple jboss processes, then you need two loops:
#!/bin/bash
Sleep1 = $1
# sleep for the first requested time
sleep = $Sleep1
# Do all the tomcat jstacks
for pid in $(ps -ef | grep java| grep "tomcat" | awk '{print $2}')
do
jstack $pid > jstack.tomcat.${pid}.txt )
done
# sleep for another 60secs
sleep 60
# Do all the jboss jstacks
for pid in $(ps -ef | grep java| egrep "jboss|JBoss" | awk '{print $2}')
do
jstack $pid > jstack.jboss.${pid}.txt )
done
Or some combinations of these methods could be used depending on exactly what you are after.