Ubuntu Bash Script PID Problems

tech-it-^ · 10-15-2009, 11:42 PM

Hello all,

I'm trying to right a bash script. Part of it requires me to write a timeout function. Now... I'm not entirely sure how to do this. I found some code and deciphered it, but it's not running correctly. What I am doing is sending two args to my script. A utility and the time-out time. I then need to grab the PID of the utility after executing it in the script. I thought a simple $! would work on getting the PID... But it doesn't. I just get the error:

kill (line number): No Such Process

As you see this doesn't help me at all. Here's the code. Please take a look.

Code:

#!/bin/bash

   #[ $# -eq 2 ] || die "cmd_timeout takes 2 arguments" 
   #command=$1
   sleep_time=$2

   # run $command in background, sleep for our timeout then kill the process if it is running
   # $! has the pid of the backgrounded job
   grep marking &
   cmd_pid=$!
   ps -ef

   # sleep for our timeout then kill the process if it is running
   (sleep $sleep_time && kill -9 $cmd_pid) &
   killer_pid=$!
   echo $killer_pid this is it

   # 'wait' for cmd_pid to complete normally.  If it does before the timeout is reached, then
   # the status will be zero.  If the killer_pid terminates it, then it will have a non-zero 
   # exit status
   wait $cmd_pid &> /dev/null
   wait_status=$?
   echo $cmd_pid

   echo $wait_status is here

   if [ $wait_status -ne 0 ]; then 
      echo "WARNING - command, $command, unclean exit" 
   else
      # Normal exit, detach and clean up the useless killer_pid
      disown $killer_pid
      kill $killer_pid &> /dev/null
   fi

As fair as I see, it looks just fine to me. No PID gets generated for the "grep" command, or it does but it doesn't show up after typing ps -ef. Then it throws that error I mentioned. Please take a look. I need this to work. Thank you!

tech-it-^ · 10-16-2009, 04:44 PM

Heres some info... When I run certain commands such as ls -R from the console and then try to look it up in ps -ef process table. It isn't there even thought I can still see it running in the other terminal. I can see the process of a grep command on the table with I run it solely in terminal but I cannot see the process run when I have the grep command embedded in a script. Whats going on?

Also I tried out the code with using vi ... It worked perfectly. So why does it work for some but not for all utilities? Thanks for the help.

tech-it-^ · 10-16-2009, 07:31 PM

I think the sleep command kills the command that I give just before it gets to the sleep command. How can this be? All the help I can get would be appreciated. Thanks!

**wmorri** · 10-18-2009, 11:32 AM

Just to let you know it is possible that we don't know the answer to your question. I don't know if you have tried searching on google yet but that is just a thought.

tech-it-^ · 10-18-2009, 11:51 AM

yes, I've been searching for hours upon hours. I even checked with my CS prof and he said it "looks" just fine, unfortunatley, he didn't have time to diagnose the problem. I just wondered why when I run certain processes and then run a process after it, it cancels the process. If no one knows the answer, thats fine. It's just frusterating.

I found if I put "env" before the sleep command, that it works for some processes but not all. Here's a seperate question:
In my scipt I need to output the contents of the a cprogram to a untility (such as cat, find, etc...). As of now I have it as

cprogram arg1 arg2 | cat

it doesnt work like I thought it would though. if I do cat cprog arg1 arg2 it seems like it works but I thought that the pipe would take the standard output of the c program (which is to the monitor/console) and direct it to the cat command. So... Any suggestions? Thanks.

shawkins · 10-28-2009, 11:14 AM

If I'm not misunderstanding your question, I think something like

ps -elf | grep $1 | grep -v "grep" | awk '{ print $4 }' | xargs kill -9

Here's how it works, step by step:

1. ps -elf : grab all the running processes
2. grep $1 : from results of step 1, pull out the line(s) that match the 1st argument to your script
3. grep -v "grep" : from the results of step 2, filter out any containing the word grep. This is to prevent this command from killing itself
4. awk '{ print $4 }' : from the results of step 3, pull out the 4th space-separated entry on the line. This should be the PID you want. IMPORTANT: you need a space between '{ and "print". Awk is fussy.
5. xargs kill -9 : xargs takes whatever it gets from stdin (which, in this case, is the output from step 4) and runs the command specified on the command line (in this case "kill -9") using the stdin stuff as arguments to that command.

Hope that helps.

tech-it-^ · 11-09-2009, 12:34 PM

This gives me the same problem when I tried it. I just added the env keyword in from of the sleep command and it works for the most part. I should of just did everything in C. Probably wouldn't of been as buggy. Fuzzer program works though. Thanks for the help guys.

10-15-2009, 11:42 PM	#1 (permalink)
tech-it-^ Registered User Join Date: Aug 2006 Posts: 320 OS: XP Pro, Vista Business, Suse Linux, Win98 SE	Ubuntu Bash Script PID Problems Hello all, I'm trying to right a bash script. Part of it requires me to write a timeout function. Now... I'm not entirely sure how to do this. I found some code and deciphered it, but it's not running correctly. What I am doing is sending two args to my script. A utility and the time-out time. I then need to grab the PID of the utility after executing it in the script. I thought a simple $! would work on getting the PID... But it doesn't. I just get the error: kill (line number): No Such Process As you see this doesn't help me at all. Here's the code. Please take a look. Code: #!/bin/bash #[ $# -eq 2 ] \|\| die "cmd_timeout takes 2 arguments" #command=$1 sleep_time=$2 # run $command in background, sleep for our timeout then kill the process if it is running # $! has the pid of the backgrounded job grep marking & cmd_pid=$! ps -ef # sleep for our timeout then kill the process if it is running (sleep $sleep_time && kill -9 $cmd_pid) & killer_pid=$! echo $killer_pid this is it # 'wait' for cmd_pid to complete normally. If it does before the timeout is reached, then # the status will be zero. If the killer_pid terminates it, then it will have a non-zero # exit status wait $cmd_pid &> /dev/null wait_status=$? echo $cmd_pid echo $wait_status is here if [ $wait_status -ne 0 ]; then echo "WARNING - command, $command, unclean exit" else # Normal exit, detach and clean up the useless killer_pid disown $killer_pid kill $killer_pid &> /dev/null fi As fair as I see, it looks just fine to me. No PID gets generated for the "grep" command, or it does but it doesn't show up after typing ps -ef. Then it throws that error I mentioned. Please take a look. I need this to work. Thank you! Last edited by shuuhen; 10-18-2009 at 01:19 PM. Reason: Language

10-16-2009, 04:44 PM	#2 (permalink)
tech-it-^ Registered User Join Date: Aug 2006 Posts: 320 OS: XP Pro, Vista Business, Suse Linux, Win98 SE	Re: Ubuntu Bash Script PID Problems Heres some info... When I run certain commands such as ls -R from the console and then try to look it up in ps -ef process table. It isn't there even thought I can still see it running in the other terminal. I can see the process of a grep command on the table with I run it solely in terminal but I cannot see the process run when I have the grep command embedded in a script. Whats going on? Also I tried out the code with using vi ... It worked perfectly. So why does it work for some but not for all utilities? Thanks for the help.

10-16-2009, 07:31 PM	#3 (permalink)
tech-it-^ Registered User Join Date: Aug 2006 Posts: 320 OS: XP Pro, Vista Business, Suse Linux, Win98 SE	Re: Ubuntu Bash Script PID Problems I think the sleep command kills the command that I give just before it gets to the sleep command. How can this be? All the help I can get would be appreciated. Thanks!

10-18-2009, 11:32 AM	#4 (permalink)
wmorri Moderator/Fedora Amb. Join Date: May 2008 Location: /pm/etc Posts: 2,805 OS: Window 7/Fedora 10 My System	Re: Ubuntu Bash Script PID Problems Just to let you know it is possible that we don't know the answer to your question. I don't know if you have tried searching on google yet but that is just a thought. __________________ Linux Forever!

10-18-2009, 11:51 AM	#5 (permalink)
tech-it-^ Registered User Join Date: Aug 2006 Posts: 320 OS: XP Pro, Vista Business, Suse Linux, Win98 SE	Re: Ubuntu Bash Script PID Problems yes, I've been searching for hours upon hours. I even checked with my CS prof and he said it "looks" just fine, unfortunatley, he didn't have time to diagnose the problem. I just wondered why when I run certain processes and then run a process after it, it cancels the process. If no one knows the answer, thats fine. It's just frusterating. I found if I put "env" before the sleep command, that it works for some processes but not all. Here's a seperate question: In my scipt I need to output the contents of the a cprogram to a untility (such as cat, find, etc...). As of now I have it as cprogram arg1 arg2 \| cat it doesnt work like I thought it would though. if I do cat cprog arg1 arg2 it seems like it works but I thought that the pipe would take the standard output of the c program (which is to the monitor/console) and direct it to the cat command. So... Any suggestions? Thanks.

10-28-2009, 11:14 AM	#6 (permalink)
shawkins Registered User Join Date: Oct 2009 Posts: 2 OS: xp	Re: Ubuntu Bash Script PID Problems If I'm not misunderstanding your question, I think something like ps -elf \| grep $1 \| grep -v "grep" \| awk '{ print $4 }' \| xargs kill -9 Here's how it works, step by step: 1. ps -elf : grab all the running processes 2. grep $1 : from results of step 1, pull out the line(s) that match the 1st argument to your script 3. grep -v "grep" : from the results of step 2, filter out any containing the word grep. This is to prevent this command from killing itself 4. awk '{ print $4 }' : from the results of step 3, pull out the 4th space-separated entry on the line. This should be the PID you want. IMPORTANT: you need a space between '{ and "print". Awk is fussy. 5. xargs kill -9 : xargs takes whatever it gets from stdin (which, in this case, is the output from step 4) and runs the command specified on the command line (in this case "kill -9") using the stdin stuff as arguments to that command. Hope that helps. Last edited by shawkins; 10-28-2009 at 11:26 AM.

11-09-2009, 12:34 PM	#7 (permalink)
tech-it-^ Registered User Join Date: Aug 2006 Posts: 320 OS: XP Pro, Vista Business, Suse Linux, Win98 SE	Re: Ubuntu Bash Script PID Problems This gives me the same problem when I tried it. I just added the env keyword in from of the sleep command and it works for the most part. I should of just did everything in C. Probably wouldn't of been as buggy. Fuzzer program works though. Thanks for the help guys.