i was looking at the solution of Run cron job only if it isn't already running in order to apply it to a similar problem that I have but I cannot understand the
ps -u $USER -f | grep "[ ]$(cat ${PIDFILE})[ ]"'
It appears to be saying check the end of each line from ps for ' PIDnumber ' but when I look at my ps output the PIDnumber is in column two. I am interpreting the first $ as the regular expression check_end_of_line option.
$(stuff) will execute "stuff" (in this case cat ${PIDFILE})
PIDFILE is assumed to be a path to a file, so the whole line is basically looking for any line in the ps output that contains the contents of the "pid file" ([ ] adds some spaces on each side of the pid so that if pid file contains '888' it wont match '8888' in the ps output)
Related
My question is :
How do I find all the running processes that end with "sh".
I know that "ps aux" lists all the processes that are running and also "grep" prints a specific named process which is written inside " ".
I know I have to combine the command "ps aux" and also "grep" with a wildcard.
My solution is ps aux | grep "*sh" but it does not run properly.
How could it be solved?
Try: ps aux | grep "sh$"
The "$" sign is regular expression that is used for pattern match at the end of the line. In this case, the pattern is "sh" so we used "sh$"
Suggesting to use pgrep command. See here.
pgrep -f "sh$"
Will return list of pids
pgrep -af "sh$"
Will return list of pids and commands
When I do
ps -ax|grep myApp
I get the one line with PID and stuff of my app.
Now, I'ld liked to process the whole result of ps -ax (without grep, so, the full output):
Either store it in a variable and grep from it later
Or go through the results in a for loop, e.g. like that:
for a in $(ps -ax)
do
echo $a
done
Unfortunally, this splits with every space, not with newline as |grep does it.
Any ideas, how I can accomplish one or the other (grep from variable or for loop)?
Important: No bash please, only POSIX, so #!/bin/sh
Thanks in advance
Like stated above, while loop can be helpful here.
One more useful thing is --no-headers argument which makes ps skip the header.
Or - even better - specify the exact columns you need to process, like ps -o pid,command --no-header ax
The overall code would look like
processes=`ps --no-headers -o pid,command ax`
echo "$processes" | while read pid command; do
echo "we have process with pid $pid and command line $command"
done
The only downside to this approach is that commands inside while loop will be executed in subshell so if you need to export some var to the parent process you'll have to do it using inter-process communication stuff.
I usually dump the results into temp file created before while loop and read them after the loop is finished.
I found a solution by removing the spaces while executing the command:
result=$(ps -aux|sed 's/ /_/g')
You can also make it more filter friendly by removing duplicated spaces:
result=$(ps -aux| tr -s ' '|sed 's/ /_/g')
I'm writing a bash script to get all process data. I'm using the following command
ps -eaf -o %cpu,%mem,acflag,acflg,args,blocked,comm,command,cpu,cputime,etime,f,flags,gid,group,inblk,inblock,jobc,ktrace,ktracep,lim,login,logname,lstart,majflt,minflt,msgrcv,msgsnd,ni,nice,nivcsw,nsignals,nsigs,nswap,nvcsw,nwchan,oublk,oublock,p_ru,paddr,pagein,pcpu,pending,pgid,pid,pmem,ppid,pri,pstime,putime,re,rgid,rgroup,rss,ruid,ruser,sess,sig,sigmask,sl,start,stat,state,stime,svgid,svuid,tdev,time,tpgid,tsess,tsiz,tt,tty,ucomm,uid,upr,user,usrpri,utime,vsize,vsz,wchan,wq,wqb,wql,wqr,xstat
What I'm trying to do is parse each line and column from this output and I'm kind of lost on where to begin. Here is the pseudo-code for what I'm wanting to do
processes = ps -aef -o ...
for i in processes
processes[i].ppid # do some stuff with this column
processes[i].pid # do some stuff with this column
processes[i].stime # do some stuff with this column
What is the best way to easily work with the output of this ps command?
Pipe the output to a loop that reads each column.
ps -aef -o ... | while read cpu mem acflag acflg args ...
do
echo "$cpu"
echo "$pid"
...
done
However, this is not going to work well with fields like args, since they have embedded whitespace and read uses whitespace as its delimiter.
This is the exact question: Append to a file in your home directory called 'water.txt' a list of all processes that have the string 'er' at the end of their name.
I know the command to list running process are ps -A, or top but the hard part is the appending only certain processes to a new file based on pattern match
The two commands that come to mind are cut and grep but I don't know exactly how to combine them together especially because the list of processes are not stored in a file/ or are they?
A command that is the combination of ps and grep is called pgrep.
With that command, you can do this to list all files that end in er:
pgrep -fa 'er$'
The option '-f' is to use the "full" name of the commands, and '-a' is to list the full name of the command with the PID number.
And to redirect the output to a file, just use '>':
pgrep -f 'er$' > ~/water.txt
The ~ means to use your home directory.
If you're looking to append all processes ending with the string er, you should use a mixture of ps and grep:
ps -aux | grep 'er$' >> ~/water.txt
The $ at the end of the er string is to make sure the process finishes with those 2 characters.
When I run this command:
ps aux|awk {'print $1,$2,$3,$11'}
I get a listing of the user, PID, CPU% and the actual command.
I want to pipe all those listings into a shell script to calculate the CPU% and if greater than, say 5, then to kill the process via the PID.
I tried piping it to a simple shell script, i.e.
ps aux|awk {'print $1,$2,$3,$11'} | ./myscript
where the content of my script is:
#!/bin/bash
# testing using positional parameters
echo "$1 $2 $3 $4"
But I get a blank output. Any idea how to do this?
Many thanks!
If you use awk, you don't need an additional bash script. Also, it is a good idea to reduce the output of the ps command so you don't have to deal with extra information:
ps acxho user,pid,%cpu,cmd | awk '$3 > 5 {system("echo kill " $2)}'
Explanation
The extra ps flags I use:
c: command only, no extra arguments
h: no header, good for scripting
o: output format. In this case, only output the user, PID, %CPU, and command
The awk command compare the %CPU, which is the third column, with a threshold (5). If it is over the threshold, then issue the system command to kill that process.
Note the echo in the command. Once you are certain the scripts works the way you like, then remove the word echo from the command to execute it for real.
Your script needs to read its input
#!/bin/bash
while read a b c d; do
echo $a $b
done
I think you can get it using xargs command to pass the AWK output to your script as arguments:
ps aux|awk {'print $1,$2,$3,$11'} | xargs ./myscript
Some extra info about xargs: http://en.wikipedia.org/wiki/Xargs
When piping input from one process to another in Linux (or POSIX-compliant systems) the output is not given as arguments to the receiving process. Instead, the standard output of the first process is piped into the standard input of the other process.
Because of this, your script cannot work. $1...$n accesses variables that have been passed as arguments to it. As there are none it won't display anything. Instead, you have to read the standard input into variables with the read command (as pointed out by William).
The pipe '|' redirects the standard output of the left to the standard input of the right. In this case, the output of the ps goes to the input of awk, then the output of awk goes to the stdin of the script.
Therefore your scripts needs to read its STDIN.
#!/bin/bash
read var1 var2 var3 ...
Then you can do whatever you want with those variables.
More info, type in bash: help read
If I well understood your problem, you want to kill every process that exceeds X% of the CPU (using ps aux).
Here is the solution using AWK:
ps aux | grep -v "%CPU" | awk '{if ($3 > XXX) { print "Killing process with PID "$2", called "$4", consuming "$3"% and launched by "$1; system( "kill -9 " $2 );}}' -
Where XXX is your threshold (% of CPU).
It also prints related info to the killed process, if it is not desired just remove the print statement.
You can add some filters like: do not remove root's process...
Try putting myscript in front like this:
./myscript `ps aux|awk {'print $1,$2,$3,$11'}`