I'm trying to write a script that runs a java program "Loop", and then after 5 seconds, terminates that java program, however, it's not terminating the program when I use the "pkill" option, I'm sorry for asking such a basic question, and I have looked around the internet, but I can't find a solution. Here is my code:
#!/bin/bash
javac Loop.java
java Loop
sleep 5
pkill -n java
When I run the command pkill -n java from the terminal, as opposed to in a script, it does as I expected, why is this?
Your bash script is waiting for java to complete so you'll need to run it as a background process which will start your Loop code and then return immediately, allowing the rest of your script to run:
java Loop &
More information: http://tldp.org/LDP/abs/html/x9644.html
Since you run java Loop in foreground, the next line sleep 5 doesn't get executed until your JVM exits (which is probably never, if Loop is actually an infinite loop).
So you need to start that in background:
java Loop &
Also, for killing that specific background job (rather than killing the newest JVM), you can do:
kill $!
Related
I am testing a bash script I hope to run as a cron job to scan a download log and perform labor-intensive conversions on image files. In order to run several conversions at once, the first script loops through the download log and sends the filename to the second script, which I set to run as a background process using &.
The script pair works well, but when the process is complete, I must press the enter key to return to a command prompt. This is a non-issue when I am running a test, but I am not sure if this behavior has ramifications when run as a cron job.
Will this be an issue? If so, is there a way to close the "terminal" running the first script from the crontab?
Here's a truncated form of my code:
Script 1 (to be launched by crontab):
for i in file1 file2 file3 etc
do
bash /path/to/convert.sh $i &
done
exit 0
Script 2 (convert.sh)
fileName=${1?no file given}
jpegName=$(echo $fileName | sed s/tif/jpg/g)
convert $fileName $jpegName
exit 0
Thanks for any help/assurances you can give!
you don't need script 2. you can convert it to function and put it inside script1.
Another problem is you are running convert.sh in an uncontrolled way. You cannot foresee how many processes will be created (background processes) and this may lead to severe performance overheads.
finally, if you cannot end process in normal way, you may choose to terminate it again using cron by issueing pkill script1.sh
I have a bash script which will be running a main command, let's say for one hour. I would like to execute another command after a certain time since the main command has been started (at t_x). Something like this:
main starts -------> main ends
|
|
at time t_x, second command is executed
At the moment I have something like this:
mpirun main_command & sleep 1m && second_command
and the problem is that after second command is executed, the main command is killed. Can anyone help me? Thanks!
The first command is failing to lock the console, as another process is also using it. You will need to redirect the standard io pipelines, 0<&- mpirun main_command >/dev/null 2>/dev/null If this still does not work, use shell -c 'mpirun main_command' & sleep 1m;second_command You can use ; instead of &&, unless you need a failing exit code when someone interrupts the sleep.
Ive got a script that takes a quite a long time to run, as it has to handle many thousands of files. I want to make this script as fool proof as possible. To this end, I want to check if the user ran the script using nohup and '&'. E.x.
me#myHost:/home/me/bin $ nohup doAlotOfStuff.sh &. I want to make 100% sure the script was run with nohup and '&', because its a very painful recovery process if the script dies in the middle for whatever reason.
How can I check those two key paramaters inside the script itself? and if they are missing, how can I stop the script before it gets any farther, and complain to the user that they ran the script wrong? Better yet, is there way I can force the script to run in nohup &?
Edit: the server enviornment is AIX 7.1
The ps utility can get the process state. The process state code will contain the character + when running in foreground. Absence of + means code is running in background.
However, it will be hard to tell whether the background script was invoked using nohup. It's also almost impossible to rely on the presence of nohup.out as output can be redirected by user elsewhere at will.
There are 2 ways to accomplish what you want to do. Either bail out and warn the user or automatically restart the script in background.
#!/bin/bash
local mypid=$$
if [[ $(ps -o stat= -p $mypid) =~ "+" ]]; then
echo Running in foreground.
exec nohup $0 "$#" &
exit
fi
# the rest of the script
...
In this code, if the process has a state code +, it will print a warning then restart the process in background. If the process was started in the background, it will just proceed to the rest of the code.
If you prefer to bailout and just warn the user, you can remove the exec line. Note that the exit is not needed after exec. I left it there just in case you choose to remove the exec line.
One good way to find if a script is logging to nohup, is to first check that the nohup.out exists, and then to echo to it and ensure that you can read it there. For example:
echo "complextag"
if ( $(cat nohup.out | grep "complextag" ) != "complextag" );then
# various commands complaining to the user, then exiting
fi
This works because if the script's stdout is going to nohup.out, where they should be going (or whatever out file you specified), then when you echo that phrase, it should be appended to the file nohup.out. If it doesn't appear there, then the script was nut run using nohup and you can scold them, perhaps by using a wall command on a temporary broadcast file. (if you want me to elaborate on that I can).
As for being run in the background, if it's not running you should know by checking nohup.
I have a bash script with a loop that calls a hard calculation routine every iteration. I use the results from every calculation as input to the next. I need make bash stop the script reading until every calculation is finished.
for i in $(cat calculation-list.txt)
do
./calculation
(other commands)
done
I know the sleep program, and i used to use it, but now the time of the calculations varies greatly.
Thanks for any help you can give.
P.s>
The "./calculation" is another program, and a subprocess is opened. Then the script passes instantly to next step, but I get an error in the calculation because the last is not finished yet.
If your calculation daemon will work with a precreated empty logfile, then the inotify-tools package might serve:
touch $logfile
inotifywait -qqe close $logfile & ipid=$!
./calculation
wait $ipid
(edit: stripped a stray semicolon)
if it closes the file just once.
If it's doing an open/write/close loop, perhaps you can mod the daemon process to wrap some other filesystem event around the execution? `
#!/bin/sh
# Uglier, but handles logfile being closed multiple times before exit:
# Have the ./calculation start this shell script, perhaps by substituting
# this for the program it's starting
trap 'echo >closed-on-calculation-exit' 0 1 2 3 15
./real-calculation-daemon-program
Well, guys, I've solved my problem with a different approach. When the calculation is finished a logfile is created. I wrote then a simple until loop with a sleep command. Although this is very ugly, it works for me and it's enough.
for i in $(cat calculation-list.txt)
do
(calculations routine)
until [[ -f $logfile ]]; do
sleep 60
done
(other commands)
done
Easy. Get the process ID (PID) via some awk magic and then use wait too wait for that PID to end. Here are the details on wait from the advanced Bash scripting guide:
Suspend script execution until all jobs running in background have
terminated, or until the job number or process ID specified as an
option terminates. Returns the exit status of waited-for command.
You may use the wait command to prevent a script from exiting before a
background job finishes executing (this would create a dreaded orphan
process).
And using it within your code should work like this:
for i in $(cat calculation-list.txt)
do
./calculation >/dev/null 2>&1 & CALCULATION_PID=(`jobs -l | awk '{print $2}'`);
wait ${CALCULATION_PID}
(other commands)
done
I have a program that runs as a daemon, using the C command fork(). It creates a new instance that runs in the background. The main instance exists after that.
What would be the best option to check if the service is running? I'm considering:
Create a file with the process id of the program and check if it's running with a script.
Use ps | grep to find the program in the running proccess list.
Thanks.
I think it will be better to manage your process with supervisord, or other process control system.
Create a cron job that runs every few minutes (or whatever you're comfortable with) and does something like this:
/path/to/is_script_stopped.sh && /path/to/script.sh
Write is_script_stopped.sh using any of the methods that you suggest. If your script is stopped cron will evaluate your script, if not, it won't.
To the question, you gave in the headline:
This simple endless loop will restart yourProgram as soon as it fails:
#!/bin/bash
for ((;;))
do
yourProgram
done
If your program depends on a resource, which might fail, it would be wise to insert a short pause, to avoid, that it will catch all system resources when failing million times per second:
#!/bin/bash
for ((;;))
do
yourProgram
sleep 1
done
To the question from the body of your post:
What would be the best option to check if the service is running?
If your ps has a -C option (like the Linux ps) you would prefer that over a ps ax | grep combination.
ps -C yourProgram