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

Question

I have a process that fails regularly  amp  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  amp  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  amp  write NOK  amp  Time to log  var processlog check  if answer   2  Do nothing  amp  write OK  amp  time to log  var processlog check  if answer   4  stot  amp  restart the process  amp  write NOK  amp  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

User · Accepted Answer

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 &

cccam oscam

User · Answer

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    gt  gt   logfile      usr local bin oscam1 -b -c  usr local etc oscam1 -t  usr local tmp oscam1  amp         2   echo  oscam1 running  all OK        date    gt  gt   logfile            echo  multiple instances of oscam1 running  Stopping  amp  restarting oscam1        date    gt  gt   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

User · Answer

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

User · Answer

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    gt  gt   logfile      usr local bin oscam1 -b -c  usr local etc oscam1 -t  usr local tmp oscam1  amp         2   echo  oscam1 running  all OK        date    gt  gt   logfile            echo  multiple instances of oscam1 running  Stopping  amp  restarting oscam1        date    gt  gt   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

User · Answer

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

User · Answer

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

User · Answer

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    gt  gt   logfile      restart-script sh    1   echo  script Running        date    gt  gt   logfile        echo  Removed duplicate instances of script    date    gt  gt   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

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

Programs to monitor if a process on a system is running.

This works with if process is not running or process is running multiple times:

A simpler version. This just test if process is running, and if not restart it.

And at last, a one liner

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