POSIX-ly finding a specific Java process

Question

In this code I find a list all of the running java processes and give the below function a name to look for, it will do its best. But since I find my approach a little too ugly, could some POSIX shell script writer have a look and possibly give me some simplification recommendations?

---

#!/bin/sh
# here is an ugly constant vuze java process name
readonly vuze_java_process_name='org.gudy.azureus2.ui.swt.Main'
is_java_program_running()
# expected arguments:
# 1ドル = java program name
{
 # there will always be at least one java process:
 # jdk.jcmd/sun.tools.jps.Jps, which is actually
 # the program giving us the list of java processes
 java_process_list=$( jps -l | awk '{print 2ドル}' )
 # this behaves strangely if there is zero processes (needs verification)
 # but since there is always at least one, no problem here
 java_process_list_count=$(( $( printf '%s\n' "${java_process_list}" | wc -l ) ))
 # set the result value as if we did not find it
 result=false
 # POSIX-ly simulate FOR loop
 i=1; while [ "${i}" -le "${java_process_list_count}" ]
 do
 # here we take one line from the list on $i position
 java_process_entry=$( echo "${java_process_list}" | sed --posix --quiet "${i}{p;q}" )
 # compare the given process entry with given java program name
 if [ "${java_process_entry}" = "${1}" ]
 then
 # set the result value
 result=true
 # end this loop
 break
 fi
 # increase iterator
 i=$(( i + 1 ))
 done
 # depending on if we found vuze process running,
 # return positive or negative result value
 if [ "${result}" = true ]
 then
 return 0
 else
 return 1
 fi
}
###
### EXAMPLE on Vuze
###
# keep Vuze alive forever, check in 5 seconds interval
while true
do
 sleep 5s
 if ! is_java_program_running "${vuze_java_process_name}"
 then
 my_date_time=$(date +%Y-%m-%d_%H:%M:%S)
 printf '%s %s\n' "${my_date_time}" "(re-)starting Vuze"
 ( /home/vlastimil/Downloads/vuze/vuze > /dev/null 2>&1 & )
 fi
done

Answer 1

Instead of simulating a for (( expr1 ; expr2 ; expr3 )) loop, use a POSIX

 for java_process_entry in $java_process_list

Notice that now you don't need to compute the number of lines, neither invoke sed.

---

There is noting wrong with early return. return 0 as soon as the desired process is found.

---

There is no need to store the entire list in a variable, neither invoke awk. Process the jps output sequentially.

All that said, consider

 is_java_program_running()
 {
 jps -l | while read pid java_process_entry; do
 if [ $java_process_entry = "${1}" ]; then return 0; fi
 done
 return 1
 }

Answer 2

(On top of what @vnp already wrote.)

---

When these lines are the last in a function:

if [ "${result}" = true ]
then
 return 0
else
 return 1
fi

Then you can write simply:

[ "${result}" = true ]

Because the exit code of a function is the exit code of its last executed statement.

• Toby Speight: In fact, given that the only other possible value of $result is false, we can just expand and execute it.