how to figure out if process is really running or waiting to run on Linux?
This is purely academic question, I don’t really need to know this information for anything, but I would like to understand kernel a bit more 🙂 According to kernel documentation http://www.tldp.org/LDP/tlk/kernel/processes.html processes in linux kernel have following states:
Running
The process is either running (it is the current process in the system) or it is ready to run (it is waiting to be assigned to one of the system’s CPUs).
Waiting
The process is waiting for an event or for a resource. Linux differentiates between two types of waiting process; interruptible and uninterruptible. Interruptible waiting processes can be interrupted by signals whereas uninterruptible waiting processes are waiting directly on hardware conditions and cannot be interrupted under any circumstances.
Stopped
The process has been stopped, usually by receiving a signal. A process that is being debugged can be in a stopped state.
Zombie
This is a halted process which, for some reason, still has a task_struct data structure in the task vector. It is what it sounds like, a dead process.
As you can see, when I take a snapshot of processes state, using command like ps , I can see, if it’s in Running state, that process either was literally Running or just waiting to be assigned to some CPU by kernel. In my opinion, these 2 states (that are actually both represented by 1 state in task_struct ) are quite different. Why there is no state like «Ready» that would mean the process is «ready to run» but wasn’t assigned to any CPU so far, so that the task_struct would be more clear about the real state? Is it even possible to retrieve this information, or is it secret for whatever reason which process is «literally running» on the CPU?
How to check the process is already running or not
I want to check the particular process in already running or not. I refereed this Q&A. But I didn’t get any specific solution. Following is the example that I tried: I have created abc.sh file and run this script on background, like sh abc.sh & . Now this file is running on background and I fire the ps aux | grep «abc» command. Following is the output of this command:
prakash 3594 0.0 0.0 4388 820 pts/0 S+ 16:44 0:00 grep --color=auto abc After that I stop the abc.sh running script and fire the same command ps aux | grep «abc» command. But I am getting same output like:
prakash 3594 0.0 0.0 4388 820 pts/0 S+ 16:44 0:00 grep --color=auto abc 7 Answers 7
Every process will be listed in the output of ps aux ; whether running, sleeping, zombie or stopped.
However, in your case, since you ran the process using sh abc.sh , sh is the application(shell) that is running and not abc.sh . Hence, ps aux will not contain the process abc.sh because of which grep could not yield any result.
So, the correct way you should have used it is as:
This may also return you other process that are running having the string sh anywhere in their output of ps aux .
You should note that the process will be «running» when the output of ps aux has its STAT as R . If it is something other than that, it is not running at the instance you fired the command to check the running processes. The different process states can be found in the man page for ps:
D uninterruptible sleep (usually IO) R running or runnable (on run queue) S interruptible sleep (waiting for an event to complete) T stopped, either by a job control signal or because it is being traced W paging (not valid since the 2.6.xx kernel) X dead (should never be seen) Z defunct ("zombie") process, terminated but not reaped by its parent You could as well run the top command to check if the process is running or sleeping and the amount of CPU, RAM it is consuming. (This will again list your process as sh ).
However, if you do want your process to be listed as abc.sh , then you should have the first line of the script you are running as:
so that the shell will know what application to use to run the script(sh in this case, change it to #!/bin/bash for bash) and then provide executable permissions to the process using:
replacing /path/to/ with the location of the abc.sh file and then run abc.sh using
again replacing /path/to/ with the location of the abc.sh file.
Bash script to check running process [duplicate]
I wrote a bash-script to check if a process is running. It doesn’t work since the ps command always returns exit code 1. When I run the ps command from the command-line, the $? is correctly set, but within the script it is always 1. Any idea?
#!/bin/bash SERVICE=$1 ps -a | grep -v grep | grep $1 > /dev/null result=$? echo "exit code: $" if [ "$" -eq "0" ] ; then echo "`date`: $SERVICE service running, everything is fine" else echo "`date`: $SERVICE is not running" fi Could you just check to see if you get non-empty output from the grep command instead of relying on return values?
I tried this and have a similar problem. The output is not taken into account. Here the code: #!/bin/bash SERVICE=$1 OUTPUT=$(ps -a | grep -v grep | grep $1) echo $OUTPUT if [ «$<#OUTPUT>» -gt 0 ] ; then echo » date : $SERVICE service running, everything is fine» else echo » date : $SERVICE is not running» fi
15 Answers 15
There are a few really simple methods:
pgrep procname && echo Running pgrep procname || echo Not running killall -q -0 procname && echo Running pidof procname && echo Running Your method will return a result even if a process just contains the process name you’re looking for. It’s not a solution to check with exact name.
This trick works for me. Hope this could help you. Let’s save the followings as checkRunningProcess.sh
#!/bin/bash ps_out=`ps -ef | grep $1 | grep -v 'grep' | grep -v $0` result=$(echo $ps_out | grep "$1") if [[ "$result" != "" ]];then echo "Running" else echo "Not Running" fi Make the checkRunningProcess.sh executable.And then use it.
Example to use.
20:10 $ checkRunningProcess.sh proxy.py Running 20:12 $ checkRunningProcess.sh abcdef Not Running this is what I needed to check if process running by it’s command line arguments as well. what is the difference ps aux vs ps -ef
I tried your version on BASH version 3.2.29, worked fine. However, you could do something like the above suggested, an example here:
#!/bin/sh SERVICE="$1" RESULT=`ps -ef | grep $1 | grep -v 'grep' | grep -v $0` result=$(echo $ps_out | grep "$1") if [[ "$result" != "" ]];then echo "Running" else echo "Not Running" fi I tried it out, doesn’t work neither. There must be something fishy with my environment (a shared hosting provider).
nothing special: the output is + SERVICE=rails + ps -a + grep -v grep + grep rails + result=1 + echo ‘exit code: 1’ exit code: 1 + ‘[‘ 1 -eq 0 ‘]’ ++ date + echo ‘Tue May 25 06:52:25 EDT 2010: rails is not running’
Just a heads up: ps -a only lists processes of the user in the current terminal. However, ps -A checks for ALL PROCESSES.
I use this one to check every 10 seconds process is running and start if not and allows multiple arguments:
#!/bin/sh PROCESS="$1" PROCANDARGS=$* while : do RESULT=`pgrep $` if [ "$" = null ]; then echo "$ not running, starting "$PROCANDARGS $PROCANDARGS & else echo "running" fi sleep 10 done Check if your scripts name doesn’t contain $SERVICE. If it does, it will be shown in ps results, causing script to always think that service is running. You can grep it against current filename like this:
#!/bin/sh SERVICE=$1 if ps ax | grep -v grep | grep -v $0 | grep $SERVICE > /dev/null then echo "$SERVICE service running, everything is fine" else echo "$SERVICE is not running" fi for those that want to use this as part of a script, and not as a function, change $0 to grep ps ax | grep -v grep | grep -v grep | grep $SERVICE > /dev/null
!/bin/bash CHECK=$0 SERVICE=$1 DATE=`date` OUTPUT=$(ps aux | grep -v grep | grep -v $CHECK |grep $1) echo $OUTPUT if [ "$" -gt 0 ] ; then echo "$DATE: $SERVICE service running, everything is fine" else echo "$DATE: $SERVICE is not running" fi
pgrep is a better solution, you still have the problem that you do not check the process name but the whole output of ps aux.
Despite some success with the /dev/null approach in bash. When I pushed the solution to cron it failed. Checking the size of a returned command worked perfectly though. The ampersrand allows bash to exit.
#!/bin/bash SERVICE=/path/to/my/service result=$(ps ax|grep -v grep|grep $SERVICE) echo $ if $> 0 then echo " Working!" else echo "Not Working. Restarting" /usr/bin/xvfb-run -a /opt/python27/bin/python2.7 SERVICE & fi #!/bin/bash ps axho comm| grep $1 > /dev/null result=$? echo "exit code: $" if [ "$" -eq "0" ] ; then echo "`date`: $SERVICE service running, everything is fine" else echo "`date`: $SERVICE is not running" /etc/init.d/$1 restart fi
Those are helpful hints. I just needed to know if a service was running when I started the script, so I could leave the service in the same state when I left. I ended up using this:
HTTPDSERVICE=$(ps -A | grep httpd | head -1) [ -z "$HTTPDSERVICE" ] && echo "No apache service running." I found the problem. ps -ae instead ps -a works.
I guess it has to do with my rights in the shared hosting environment. There’s apparently a difference between executing «ps -a» from the command line and executing it from within a bash-script.
A simple script version of one of Andor’s above suggestions:
!/bin/bash pgrep $1 && echo Running If the above script is called test.sh then, in order to test, type: test.sh NameOfProcessToCheck
I was wondering if it would be a good idea to have progressive attempts at a process, so you pass this func a process name func_terminate_process «firefox» and it tires things more nicely first, then moves on to kill.
# -- NICE: try to use killall to stop process(s) killall $ > /dev/null 2>&1 ;sleep 10 # -- if we do not see the process, just end the function pgrep $ > /dev/null 2>&1 || return # -- UGLY: Step trough every pid and use kill -9 on them individually for PID in $(pidof $) ;do echo "Terminating Process: [$], PID [$]" kill -9 $ ;sleep 10 # -- NASTY: If kill -9 fails, try SIGTERM on PID if ps -p $ > /dev/null ;then echo "$ is still running, forcefully terminating with SIGTERM" kill -SIGTERM $ ;sleep 10 fi done # -- If after all that, we still see the process, report that to the screen. pgrep $ > /dev/null 2>&1 && echo "Error, unable to terminate all or any of [$]" || echo "Terminate process [$] : SUCCESSFUL" I need to do this from time to time and end up hacking the command line until it works.
For example, here I want to see if I have any SSH connections, (the 8th column returned by «ps» is the running «path-to-procname» and is filtered by «awk»:
ps | awk -e '< print $8 >' | grep ssh | sed -e 's/.*\///g' Then I put it in a shell-script, («eval»-ing the command line inside of backticks), like this:
#!/bin/bash VNC_STRING=`ps | awk -e '< print $8 >' | grep vnc | sed -e 's/.*\///g'` if [ ! -z "$VNC_STRING" ]; then echo "The VNC STRING is not empty, therefore your process is running." fi The «sed» part trims the path to the exact token and might not be necessary for your needs.
Here’s my example I used to get your answer. I wrote it to automatically create 2 SSH tunnels and launch a VNC client for each.
I run it from my Cygwin shell to do admin to my backend from my windows workstation, so I can jump to UNIX/LINUX-land with one command, (this also assumes the client rsa keys have already been «ssh-copy-id»-ed and are known to the remote host).
It’s idempotent in that each proc/command only fires when their $VAR eval’s to an empty string.
It appends » | wc -l» to store the number of running procs that match, (i.e., number of lines found), instead of proc-name for each $VAR to suit my needs. I keep the «echo» statements so I can re-run and diagnose the state of both connections.
#!/bin/bash SSH_COUNT=`eval ps | awk -e '< print $8 >' | grep ssh | sed -e 's/.*\///g' | wc -l` VNC_COUNT=`eval ps | awk -e '< print $8 >' | grep vnc | sed -e 's/.*\///g' | wc -l` if [ $SSH_COUNT = "2" ]; then echo "There are already 2 SSH tunnels." elif [ $SSH_COUNT = "1" ]; then echo "There is only 1 SSH tunnel." elif [ $SSH_COUNT = "0" ]; then echo "connecting 2 SSH tunnels." ssh -L 5901:localhost:5901 -f -l USER1 HOST1 sleep 10; ssh -L 5904:localhost:5904 -f -l USER2 HOST2 sleep 10; fi if [ $VNC_COUNT = "2" ]; then echo "There are already 2 VNC sessions." elif [ $VNC_COUNT = "1" ]; then echo "There is only 1 VNC session." elif [ $VNC_COUNT = "0" ]; then echo "launching 2 vnc sessions." vncviewer.exe localhost:1 & vncviewer.exe localhost:4 & fi This is very perl-like to me and possibly more unix utils than true shell scripting. I know there are lots of «MAGIC» numbers and cheezy hard-coded values but it works, (I think I’m also in poor taste for using so much UPPERCASE too). Flexibility can be added with some cmd-line args to make this more versatile but I wanted to share what worked for me. Please improve and share. Cheers.