I have a bash script running in the background, and it executes in a loop every 5 seconds. This effects the commands that are being executed at the shell itself.
Is there a way, i can suspend the script execution until the shell is not executing other commands.
thanks
to stop the scipt you can use
kill -s STOP $PID
where $PID contains the process ID of the script. To start it again, you use
kill -s CONT $PID
Renice should help in such scenario.
Using renice you can decrease/increase the priority of the process.
Look man page for more detailed help.
Related
Let's say I have a silly script:
while true;do
touch ~/test_file
sleep 3
done
And I start the script into the background and leave the terminal:
chmod u+x silly_script.sh
./silly_script.sh &
exit
Is there a way for me to identify and stop that script now? The way I see it is, that every command is started in it's own process and I might be able to catch and kill one command like the 'sleep 3' but not the execution of the entire script, am I mistaken? I expected a process to appear with the scripts name, but it does not. If I start the script with 'source silly_script.sh' I can't find a process by the name of 'source'. Do I need to identify the instance of bash, that is executing the script? How would I do that?
EDIT: There have been a few creative solutions, but so far they require the PID of the script execution to be stored right away, or the bash session to not be left with ^D or exit. I understand, that this way of running scripts should maybe be avoided, but I find it hard to believe, that any low privilege user could, even by accident, start an annoying script into the background, that is for instance filling the drive with garbage files or repeatedly starting new instances of some software and even the admin has no other option, than to restart the server, because a simple script can hide it's identifier without even trying.
With the help of the fine people here I was able to derive the answer I needed:
It is true, that the script runs every command in it's own process, so for instance killing the sleep 3 command won't do anything to the script being run, but through a command like the sleep 3 you can find the bash instance running the script, by looking for the parent process:
So after doing the above, you can run ps axf to show all processes in a tree form. You will then find this section:
18660 ? S 0:00 /bin/bash
18696 ? S 0:00 \_ sleep 3
Now you have found the bash instance, that is running the script and can stop it: kill 18660
(Of course your PID will be different from mine)
The jobs command will show you all running background jobs.
You can kill background jobs by id using kill, e.g.:
$ sleep 9999 &
[1] 58730
$ jobs
[1]+ Running sleep 9999 &
$ kill %1
[1]+ Terminated sleep 9999
$ jobs
$
58730 is the PID of the backgrounded task, and 1 is the task id of it. In this case kill 58730 and kill %1` would have the same effect.
See the JOB CONTROL section of man bash for more info.
When you exit, the backgrounded job will get a kill signal and die (assuming that's how it handles the signal - in your simple example it is), unless you disown it first.
That kill will propogate to the sleep process, which may well ignore it and continue sleeping. If this is the case you'll still see it in ps -e output, but with a parent pid of 1 indicating its original parent no longer exists.
You can use ps -o ppid= <pid> to find the parent of a process, or pstree -ap to visualise the job hierarchy and find the parent visually.
#! /bin/sh -e
cd /home/pi/projects/3._Raspberry_Client/bin/ARM/Debug
while true;
do
./3._Raspberry_Client.out
sleep 3s
done
I want to start program when it be killed.
So, I make shell script; like sample.
If Run it on bash and do kill -9 something, it perfectly works.
But I want to run this shell script on startup.
I set it in /etc/xdg/lxsession/LXDE-pi/autostart.
like,
./Client_Boot.sh (this is in /home/pi)
then I reboot, shell script works.
But If I kill the program, shell script is also being killed too.
Why this happens? And What should I do?
Thanks for your kindness. And Sry to Bad English.
I have a bash script running on Ubuntu.
Is it possible to see the line/command executed now without script restart.
The issue is that script sometimes never exits. This is really hard to reproduce (now I caught it), so I can't just stop the script and start the debugging.
Any help would be really appreciated
P.S. Script logic is hard to understand, so I can't to figure out why it's frozen by power of thoughts.
Try to find the process id (pid) of the shell, you may use ps -ef | grep <script_name>
Let's set this pid in the shell variable $PID.
Find all the child processes of this $PID by:
ps --ppid $PID
You might find one or more (if for example it's stuck in a pipelined series of commands). Repeat this command couple of times. If it doesn't change this means the script is stuck in certain command. In this case, you may attach trace command to the running child process:
sudo strace -p $PID
This will show you what is being executed, either indefinite loop (like reading from a pipe) or waiting on some event that never happens.
In case you find ps --ppid $PID changes, this indicates that your script is advancing but it's stuck somewhere, e.g. local loop in the script. From the changing commands, it can give you a hint where in the script it's looping.
I run a shell script inside php (using shell_exec). I want to kill it and all processes it created when it is in operation. I know the shell script pid. Do you have any suggestion?
I am using ubuntu, php as apache module.
Thank you.
Example:
#!/bin/bash
echo hello
sleep 20
When I kill my script (shell_exec("sudo kill -9 $pid")), the sleep process is not killed which is not desired.
use
pkill -TERM -P pid
will kill the child processes
see this answer
Use this kill command instead:
kill -- -$pid
to kill the running script and all its spawned children.
Ok, just like in this thread, How to get PID of background process?, I know how to get the PID of background process. However, what I need to do countains more than one operation.
{
sleep 300;
echo "Still running after 5 min, killing process manualy.";
COMMAND COMMAND COMMAND
echo "Shutdown complete"
}&
PID_CHECK_STOP=$!
some stuff...
kill -9 $PID_CHECK_STOP
But it doesn't work. It seems i get either a bad PID or I just can't kill it. I tried to run ps | grep sleep and the pid it gives is always right next to the one i get in PID_CHECK_STOP. Is there a way to make it work? Can i wrap those commands an other way so i can kill them all when i need to?
Thx guys!
kill -9 kills the process before it can do anything else, including signalling its children to exit. Use a gentler signal (kill by itself, which sends a TERM, should be sufficient). You do need to have the process signal its children to exit (if any) explicitly, though, via a trap command.
I'm assuming sleep is a placeholder for the real command. sleep is tricky, however, as it ignores any signals until it returns (i.e., it is non-interruptible). To make your example work, put sleep itself in the background and immediately wait on it. When you kill the "outer" background process, it will interrupt the wait call, which will allow sleep to be killed as well.
{
trap 'kill $(jobs -p)' EXIT
sleep 300 & wait
echo "Still running after 5 min, killing process manualy.";
COMMAND COMMAND COMMAND
echo "Shutdown complete"
}&
PID_CHECK_STOP=$!
some stuff...
kill $PID_CHECK_STOP
UPDATE: COMMAND COMMAND COMMAND includes a command that runs via sudo. To kill that process, kill must also be run via sudo. Keep in mind that doing so will run the external kill program, not the shell built-in (there is little difference between the two; the built-in exists to allow you to kill a process when your process quota has been reached).
You can have another script containing those commands and kill that script. If you are dynamically generating code for the block, just write out a script, execute it and kill when you are done.
The { ... } surrounding the statements starts a new shell, and you get its PID afterwards. sleep and other commands within the block get separate PIDs.
To illustrate, look for your process in ps afux | less - the parent shell process (above the sleep) has the PID you were just given.