Getting last process ID in bash script with $! doesn't always work - linux

I am a little down the rabbit hole here..
I had a little script that should just start a dotnet process into the background and save the process id.
#!/bin/bash
echo "killing $(cat ~/currentPID)"
kill `cat ~/currentPID`
export ASPNETCORE_ENVIRONMENT=Staging && cd ~/Project/bin/Debug/net6.0/ && dotnet Project.dll --urls=http://localhost:42666 &
echo "$!" > ~/currentPID
This works from time to time but most of my tries, the PID would be $! + 1
Even if I try something like this:
#!/bin/bash
echo "killing $(cat ~/currentPID)"
kill `cat ~/currentPID`
echo "killing $(cat ~/currentPID2)"
kill `cat ~/currentPID2`
echo "killing $(cat ~/currentPID3)"
kill `cat ~/currentPID3`
export ASPNETCORE_ENVIRONMENT=Staging && cd ~/Project/bin/Debug/net6.0/ && dotnet Project.dll --urls=http://localhost:42666 &
CURRPID="$!"
sleep 3
echo "$(($CURRPID + 1))" > ~/currentPID2
echo "$(($CURRPID + 2))" > ~/currentPID3
echo "$CURRPID" > ~/currentPID
it will be currentPID3 + 1
I guess I will use pkill -P but anyone got any ideas what's going on here?! :)
PS: ps aux says that currentPID is the process of the shell script itself. Which makes sense. The other PIDs will be unassigned though.

Related

Script guide to prevent duplicate execution of jar in Linux

Jar should run in the background and not run redundantly.
Even if duplicate execution occurs, all must be terminated
#!/bin/bash
ENV=dev
SER_NAME=batch
JAR_FULL=/was/batch/test.jar
case $1 in
restart)
if apid=$(pgrep -f $SER_NAME)
then
for pid in $apid; do
echo "Stop $SER_NAME pid : $pid"
kill -9 $pid
done
else
echo "$SER_NAME is not running ... "
fi
nohup java -jar $JAR_FULL --spring.profiles.active=$ENV > /dev/null 2>&1 &
echo "$SER_NAME" start"
;;
stop)
if apid=$(pgrep -f $SER_NAME)
then
for pid in $apid; do
echo "Stop $SER_NAME - pid : $pid"
kill -9 $pid
done
else
echo "$SER_NAME is not running ..."
fi
;;
start)
if apid=$(pgrep -f $SER_NAME)
then
echo "$SER_NAME is already running ..."
for pid in $apid; do
echo "Running $SER_NAME -pid : $pid"
done
else
nohup java -jar $JAR_FULL --spring.profiles.active=$ENV > /dev/null 2>&1 &
echo "$SER_NAME start!"
fi
;;
esac
example) run.sh
console) chmod 755 run.sh
console) ./run.sh start
start or stop or restart

Linux Script to check if process is running and restart if not

I am having this script which looks for the process filebeat and restarts it if is not running. Cron runs this script every 5 minutes. Most of the time this works fine except sometime it creates multiple filebeat process. Can someone please point out what is the issue in my script.
#!/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
service=filebeat
servicex=/usr/share/filebeat/bin/filebeat
pid=`pgrep -x "filebeat"`
if [ $pid > /dev/null ]
then
echo "$(date) $service is running!!!"
else
echo "$(date) starting $service"
cd /home/hpov/beats/filebeat
./filebeat -c filebeat.yml &
fi
#!/bin/bash
pidof script.x86 >/dev/null
if [[ $? -ne 0 ]] ; then
echo "Restarting script: $(date)" >> /var/log/script.txt
/etc/script/script.x86 &
fi
Super easy :D

Propagate exit code from runuser command

I want to run the bash script, StartSomething.sh, as a specific user. I use runuser command for that. Also I want to know an exit code from this bash script. So I write an exit code to the file when the command is finished or interrupted. Here is the code:
runuser myuser -s /bin/bash -c "./StartSomething.sh --pidfile=${pidfile}; \
echo $? > ${statusfile};" &
sleep 5
pid=$(cat ${pidfile})
while ps -p ${pid} > /dev/null; do sleep 1; done
end=$(cat ${statusfile})
echo "End code: ${end}"
exit ${end}
Problem is that exit code is still 0, though bash script is interrupted. What can be wrong?
If I have separate file, start.sh, with this code:
./StartSomething.sh --pidfile=${pidfile}
echo $? > ${statusfile}
and runuser command look like this:
runuser myuser -s /bin/bash -c "./start.sh" &
everything is working fine. I want to use first example without separate file. Can someone tell me what can be wrong? Is there better solution for this problem?
If all you want to do is to run the program in the background, and wait for it to finish, I think you could also use wait to get the return value (runuser passes it through, unless something exceptional happens):
runuser myuser ./StartSomething.sh --pidfile=${pidfile} &
pid=$!
# do something else
wait $!
echo "it returned $?"
or
runuser myuser ./StartSomething.sh --pidfile=${pidfile} &
pid=$!
echo -n "waiting"
while kill -0 $pid 2>/dev/null; do
echo -n "."
sleep 1
done
echo
wait $!
echo "it returned $?"
There is problem with escaping special character $. Correct command:
runuser myuser -s /bin/bash -c "./StartSomething.sh --pidfile=${pidfile}; \
echo \$? > ${statusfile};" &
Replace $? with \$?.

Background rsync and pid from a shell script

I have a shell script that does a backup. I set this script in a cron but the problem is that the backup is heavy so it is possible to execute a second rsync before the first ends up.
I thought to launch rsync in a script and then get PID and write a file that script checks if the process exist or not (if this file exist or not).
If I put rsync in background I get the PID but I don't know how to know when rsync ends up but, if I set rsync (no background) I can't get PID before the process finish so I can't write a file whit PID.
I don't know what is the best way to "have rsync control" and know when it finish.
My script
#!/bin/bash
pidfile="/home/${USER}/.rsync_repository"
if [ -f $pidfile ];
then
echo "PID file exists " $(date +"%Y-%m-%d %H:%M:%S")
else
rsync -zrt --delete-before /repository/ /mnt/backup/repositorio/ < /dev/null &
echo $$ > $pidfile
# If I uncomment this 'rm' and rsync is running in background, the file is deleted so I can't "control" when rsync finish
# rm $pidfile
fi
Can anybody help me?!
Thanks in advance !! :)
# check to make sure script isn't still running
# if it's still running then exit this script
sScriptName="$(basename $0)"
if [ $(pidof -x ${sScriptName}| wc -w) -gt 2 ]; then
exit
fi
pidof finds the pid of a process
-x tells it to look for scripts too
${sScriptName} is just the name of the script...you can hardcode this
wc -w returns the word count by words
-gt 2 no more than one instance running (instance plus 1 for the pidof check)
if more than one instance running then exit script
Let me know if this works for you.
Test both for presence of pid file and status of the running process like this:
#!/bin/bash
pidfile="/home/${USER}/.rsync_repository"
is_running =0
if [ -f $pidfile ];
then
echo "PID file exists " $(date +"%Y-%m-%d %H:%M:%S")
previous_pid=`cat $pidfile`
is_running=`ps -ef | grep $previous_pid | wc -l`
fi
if [ $is_running -gt 0 ];
then
echo "Previous process didn't quit yet"
else
rsync -zrt --delete-before /repository/ /mnt/backup/repositorio/ < /dev/null &
echo $$ > $pidfile
fi
Hope this helps!!!

Linux Script to check if process is running and act on the result

I have a process that fails regularly & sometimes starts duplicate instances..
When I run:
ps x |grep -v grep |grep -c "processname"
I will get:
2
This is normal as the process runs with a recovery process..
If I get
0
I will want to start the process
if I get:
4
I will want to stop & restart the process
What I need is a way of taking the result of ps x |grep -v grep |grep -c "processname"
Then setup a simple 3 option function
ps x |grep -v grep |grep -c "processname"
if answer = 0 (start process & write NOK & Time to log /var/processlog/check)
if answer = 2 (Do nothing & write OK & time to log /var/processlog/check)
if answer = 4 (stot & restart the process & write NOK & Time to log /var/processlog/check)
The process is stopped with
killall -9 process
The process is started with
process -b -c /usr/local/etc
My main problem is finding a way to act on the result of ps x |grep -v grep |grep -c "processname".
Ideally, I would like to make the result of that grep a variable within the script with something like this:
process=$(ps x |grep -v grep |grep -c "processname")
If possible.
Programs to monitor if a process on a system is running.
Script is stored in crontab and runs once every minute.
This works with if process is not running or process is running multiple times:
#! /bin/bash
case "$(pidof amadeus.x86 | wc -w)" in
0) echo "Restarting Amadeus: $(date)" >> /var/log/amadeus.txt
/etc/amadeus/amadeus.x86 &
;;
1) # all ok
;;
*) echo "Removed double Amadeus: $(date)" >> /var/log/amadeus.txt
kill $(pidof amadeus.x86 | awk '{print $1}')
;;
esac
0 If process is not found, restart it.
1 If process is found, all ok.
* If process running 2 or more, kill the last.
A simpler version. This just test if process is running, and if not restart it.
It just tests the exit flag $? from the pidof program. It will be 0 of process is running and 1 if not.
#!/bin/bash
pidof amadeus.x86 >/dev/null
if [[ $? -ne 0 ]] ; then
echo "Restarting Amadeus: $(date)" >> /var/log/amadeus.txt
/etc/amadeus/amadeus.x86 &
fi
And at last, a one liner
pidof amadeus.x86 >/dev/null ; [[ $? -ne 0 ]] && echo "Restarting Amadeus: $(date)" >> /var/log/amadeus.txt && /etc/amadeus/amadeus.x86 &
This can then be used in crontab to run every minute like this:
* * * * * pidof amadeus.x86 >/dev/null ; [[ $? -ne 0 ]] && echo "Restarting Amadeus: $(date)" >> /var/log/amadeus.txt && /etc/amadeus/amadeus.x86 &
cccam oscam
I adopted the #Jotne solution and works perfectly! For example for mongodb server in my NAS
#! /bin/bash
case "$(pidof mongod | wc -w)" in
0) echo "Restarting mongod:"
mongod --config mongodb.conf
;;
1) echo "mongod already running"
;;
esac
I have adopted your script for my situation Jotne.
#! /bin/bash
logfile="/var/oscamlog/oscam1check.log"
case "$(pidof oscam1 | wc -w)" in
0) echo "oscam1 not running, restarting oscam1: $(date)" >> $logfile
/usr/local/bin/oscam1 -b -c /usr/local/etc/oscam1 -t /usr/local/tmp.oscam1 &
;;
2) echo "oscam1 running, all OK: $(date)" >> $logfile
;;
*) echo "multiple instances of oscam1 running. Stopping & restarting oscam1: $(date)" >> $logfile
kill $(pidof oscam1 | awk '{print $1}')
;;
esac
While I was testing, I ran into a problem..
I started 3 extra process's of oscam1 with this line:
/usr/local/bin/oscam1 -b -c /usr/local/etc/oscam1 -t /usr/local/tmp.oscam1
which left me with 8 process for oscam1. the problem is this..
When I run the script, It only kills 2 process's at a time, so I would have to run it 3 times to get it down to 2 process..
Other than killall -9 oscam1 followed by /usr/local/bin/oscam1 -b -c /usr/local/etc/oscam1 -t /usr/local/tmp.oscam1, in *)is there any better way to killall apart from the original process? So there would be zero downtime?
If you changed awk '{print $1}' to '{ $1=""; print $0}' you will get all processes except for the first as a result. It will start with the field separator (a space generally) but I don't recall killall caring. So:
#! /bin/bash
logfile="/var/oscamlog/oscam1check.log"
case "$(pidof oscam1 | wc -w)" in
0) echo "oscam1 not running, restarting oscam1: $(date)" >> $logfile
/usr/local/bin/oscam1 -b -c /usr/local/etc/oscam1 -t /usr/local/tmp.oscam1 &
;;
2) echo "oscam1 running, all OK: $(date)" >> $logfile
;;
*) echo "multiple instances of oscam1 running. Stopping & restarting oscam1: $(date)" >> $logfile
kill $(pidof oscam1 | awk '{ $1=""; print $0}')
;;
esac
It is worth noting that the pidof route seems to work fine for commands that have no spaces, but you would probably want to go back to a ps-based string if you were looking for, say, a python script named myscript that showed up under ps like
root 22415 54.0 0.4 89116 79076 pts/1 S 16:40 0:00 /usr/bin/python /usr/bin/myscript
Just an FYI
The 'pidof' command will not display pids of shell/perl/python scripts. So to find the process id’s of my Perl script I had to use the -x option i.e. 'pidof -x perlscriptname'
I cannot get case to work at all.
Heres what I have:
#! /bin/bash
logfile="/home/name/public_html/cgi-bin/check.log"
case "$(pidof -x script.pl | wc -w)" in
0) echo "script not running, Restarting script: $(date)" >> $logfile
# ./restart-script.sh
;;
1) echo "script Running: $(date)" >> $logfile
;;
*) echo "Removed duplicate instances of script: $(date)" >> $logfile
# kill $(pidof -x ./script.pl | awk '{ $1=""; print $0}')
;;
esac
rem the case action commands for now just to test the script. the above pidof -x command is returning '1', the case statement is returning the results for '0'.
Anyone have any idea where I'm going wrong?
Solved it by adding the following to my BIN/BASH Script:
PATH=$PATH:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
In case you're looking for a more modern way to check to see if a service is running (this will not work for just any old process), then systemctl might be what you're looking for.
Here's the basic command:
systemctl show --property=ActiveState your_service_here
Which will yield very simple output (one of the following two lines will appear depending on whether the service is running or not running):
ActiveState=active
ActiveState=inactive
And if you'd like to know all of the properties you can get:
systemctl show --all your_service_here
If you prefer that alphabetized:
systemctl show --all your_service_here | sort
And the full code to act on it:
service=$1
result=`systemctl show --property=ActiveState $service`
if [[ "$result" == 'ActiveState=active' ]]; then
echo "$service is running" # Do something here
else
echo "$service is not running" # Do something else here
fi
If you are using CentOS, no need to write a script and set cron job. Here is one of the smartest ways to ensure systemd services restart on failure.
Make following changes to /usr/lib/systemd/system/mariadb.service
Then under the [Service] section in the file, add the following 2 lines:
Restart=always
RestartSec=3
After saving the file we need to reload the daemon configurations to ensure systemd is aware of the new file
systemctl daemon-reload
Read the following link for the complete steps -
https://jonarcher.info/2015/08/ensure-systemd-services-restart-on-failure/

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