BASH. Make the result of one command to be an argument of another [duplicate] - linux

This question already has answers here:
Using the result of a command as an argument in bash?
(7 answers)
Closed 5 years ago.
How can I make the result of one command to be an argument of another?
I'm trying to kill child process by pid of parent process and use for it pgrep
Example: pgrep -P <PID>
But after I need to kill the PID which I get from pgrep
pgrep -P <PID> | kill - it doesn't work(
Thank you!

With single pkill command:
pkill -P <PID> --signal SIGTERM
--signal signal
Defines the signal to send to each matched process. Either the numeric or the symbolic signal name can be
used. (pkill only.)

Try this:
VALUE="$(pgrep -P <PID>)"
kill ${VALUE}

You use backticks for that. Like this:
kill `pgrep -P <PID>`

this should work for you
kill -9 `command`
and as far as getting the pid is concerned see examples below
kill -9 `pgrep executable`
kill -9 `pgrep ps`
kill -9 `pgrep bash`
or your command
kill -9 `pgrep -P <PID>`

You probably want "kill -9" as well:
pgrep -P <PID> | xargs -n1 kill -9
To test what it is going to do in advance try:
pgrep -P <PID> | xargs -n1 echo kill -9

Related

How to extract a column value from a command output in shell script

I am trying to write a shell script where I want to kill a list of processes given by fuser command.
The output of fuser is given. I want to kill the pids listed
kill -9 157909 1504107 1504111 1504112 2690311 3206490
How do I do that?
-k, --kill
Kill processes accessing the file. Unless changed with -SIGNAL,
SIGKILL is sent. An fuser process never kills itself, but may
kill other fuser processes. The effective user ID of the
process executing fuser is set to its real user ID before
attempting to kill.
fuser -k will do it.
ps -u beadm | awk '{print $2}' | while read line; do kill -9 $line; done

How to combine "lsof -i :port" and "kill pid" in bash

How do i combine these two commands in the bash:
lsof -i :port
kill pid
The first one returns the PID i want to kill to release the port. The second one kills the returned PID.
I am doing this because I donĀ“t know of any way to kill a jetty webserver within the Netbeans IDE on OSX. Is there a way?
You can use $():
kill $(lsof -t -i:port)
You can use
kill -9 `lsof -t -i:port`

Shell script to get the process ID on Linux [duplicate]

This question already has answers here:
How to get pid given the process name
(4 answers)
Closed 5 years ago.
I want to write a shell script (.sh file) to get a given process id. What I'm trying to do here is once I get the process ID, I want to kill that process. I'm running on Ubuntu (Linux).
I was able to do it with a command like
ps -aux|grep ruby
kill -9 <pid>
but I'm not sure how to do it through a shell script.
Using grep on the results of ps is a bad idea in a script, since some proportion of the time it will also match the grep process you've just invoked. The command pgrep avoids this problem, so if you need to know the process ID, that's a better option. (Note that, of course, there may be many processes matched.)
However, in your example, you could just use the similar command pkill to kill all matching processes:
pkill ruby
Incidentally, you should be aware that using -9 is overkill (ho ho) in almost every case - there's some useful advice about that in the text of the "Useless Use of kill -9 form letter ":
No no no. Don't use kill -9.
It doesn't give the process a chance to cleanly:
shut down socket connections
clean up temp files
inform its children that it is going away
reset its terminal characteristics
and so on and so on and so on.
Generally, send 15, and wait a second or two, and if that doesn't
work, send 2, and if that doesn't work, send 1. If that doesn't,
REMOVE THE BINARY because the program is badly behaved!
Don't use kill -9. Don't bring out the combine harvester just to tidy
up the flower pot.
If you are going to use ps and grep then you should do it this way:
ps aux|grep r[u]by
Those square brackets will cause grep to skip the line for the grep command itself. So to use this in a script do:
output=`ps aux|grep r\[u\]by`
set -- $output
pid=$2
kill $pid
sleep 2
kill -9 $pid >/dev/null 2>&1
The backticks allow you to capture the output of a comand in a shell variable. The set -- parses the ps output into words, and $2 is the second word on the line which happens to be the pid. Then you send a TERM signal, wait a couple of seconds for ruby to to shut itself down, then kill it mercilessly if it still exists, but throw away any output because most of the time kill -9 will complain that the process is already dead.
I know that I have used this without the backslashes before the square brackets but just now I checked it on Ubuntu 12 and it seems to require them. This probably has something to do with bash's many options and the default config on different Linux distros. Hopefully the [ and ] will work anywhere but I no longer have access to the servers where I know that it worked without backslash so I cannot be sure.
One comment suggests grep-v and that is what I used to do, but then when I learned of the [] variant, I decided it was better to spawn one fewer process in the pipeline.
As a start there is no need to do a ps -aux | grep... The command pidof is far better to use. And almost never ever do kill -9 see here
to get the output from a command in bash, use something like
pid=$(pidof ruby)
or use pkill directly.
option -v is very important. It can exclude a grep expression itself
e.g.
ps -w | grep sshd | grep -v grep | awk '{print $1}' to get sshd id
This works in Cygwin but it should be effective in Linux as well.
ps -W | awk '/ruby/,NF=1' | xargs kill -f
or
ps -W | awk '$0~z,NF=1' z=ruby | xargs kill -f
Bash Pitfalls
You can use the command killall:
$ killall ruby
Its pretty simple.
Simply Run Any Program like this :- x= gedit & echo $! this will give you PID of this process.
then do this kill -9 $x
To kill the process in shell
getprocess=`ps -ef|grep servername`
#echo $getprocess
set $getprocess
pid=$2
#echo $pid
kill -9 $pid
If you already know the process then this will be useful:
PID=`ps -eaf | grep <process> | grep -v grep | awk '{print $2}'`
if [[ "" != "$PID" ]]; then
echo "killing $PID"
kill -9 $PID
fi

linux shell: How to read command argument from a file?

I have process id in a file "pid"
I'd like to kill it.
Something like:
kill -9 <read pid from file>
I tried:
kill -9 `more pid`
but it does not work. I also tried xargs but can't get my head around it.
Does
kill -9 $(cat pid)
work for you?
Let me summarize all answers
kill -9 $(cat pid)
kill -9 `cat pid`
cat pid | xargs kill -9
my preference is
kill -9 `cat pid`
that will work for any command in the backticks.
kill -9 $(cat pid) or cat pid | xargs kill -9 will both work
You should be starting off gradually and then move up to the heavy stuff to kill the process if it doesn't want to play nicely.
A SIGKILL (-9) signal can't be caught and that will mean that any resources being held by the process won't be cleaned up.
Try using a kill SIGTERM (-15) first and then check for the presence of the process still by doing a kill -0 $(cat pid). If it is still hanging around, then by all means clobber it with -9.
SIGTERM can be caught by a process and any process that has been properly written should have a signal handler to catch the SIGTERM and then clean up its resources before exiting.

How can I kill a process by name instead of PID, on Linux? [duplicate]

This question already has answers here:
Find and kill a process in one line using bash and regex
(30 answers)
Closed 1 year ago.
Sometimes when I try to start Firefox it says "a Firefox process is already running". So I have to do this:
jeremy#jeremy-desktop:~$ ps aux | grep firefox
jeremy 7451 25.0 27.4 170536 65680 ? Sl 22:39 1:18 /usr/lib/firefox-3.0.1/firefox
jeremy 7578 0.0 0.3 3004 768 pts/0 S+ 22:44 0:00 grep firefox
jeremy#jeremy-desktop:~$ kill 7451
What I'd like is a command that would do all that for me. It would take an input string and grep for it (or whatever) in the list of processes, and would kill all the processes in the output:
jeremy#jeremy-desktop:~$ killbyname firefox
I tried doing it in PHP but exec('ps aux') seems to only show processes that have been executed with exec() in the PHP script itself (so the only process it shows is itself.)
pkill firefox
More information: http://linux.about.com/library/cmd/blcmdl1_pkill.htm
Also possible to use:
pkill -f "Process name"
For me, it worked up perfectly. It was what I have been looking for.
pkill doesn't work with name without the flag.
When -f is set, the full command line is used for pattern matching.
You can kill processes by name with killall <name>
killall sends a signal to all
processes running any of the specified
commands. If no signal name is
specified, SIGTERM is sent.
Signals can be specified either by
name (e.g. -HUP or -SIGHUP ) or by number (e.g.
-1) or by option -s.
If the command name is not regular
expression (option -r) and contains a
slash (/), processes executing that
particular file will be selected for
killing, independent of their name.
But if you don't see the process with ps aux, you probably won't have the right to kill it ...
A bit longer alternative:
kill `pidof firefox`
The easiest way to do is first check you are getting right process IDs with:
pgrep -f [part_of_a_command]
If the result is as expected. Go with:
pkill -f [part_of_a_command]
If processes get stuck and are unable to accomplish the request you can use kill.
kill -9 $(pgrep -f [part_of_a_command])
If you want to be on the safe side and only terminate processes that you initially started add -u along with your username
pkill -f [part_of_a_command] -u [username]
Kill all processes having snippet in startup path. You can kill all apps started from some directory by for putting /directory/ as a snippet. This is quite usefull when you start several components for the same application from the same app directory.
ps ax | grep <snippet> | grep -v grep | awk '{print $1}' | xargs kill
* I would prefer pgrep if available
Strange, but I haven't seen the solution like this:
kill -9 `pidof firefox`
it can also kill multiple processes (multiple pids) like:
kill -9 `pgrep firefox`
I prefer pidof since it has single line output:
> pgrep firefox
6316
6565
> pidof firefox
6565 6316
Using killall command:
killall processname
Use -9 or -KILL to forcefully kill the program (the options are similar to the kill command).
On Mac I could not find the pgrep and pkill neither was killall working so wrote a simple one liner script:-
export pid=`ps | grep process_name | awk 'NR==1{print $1}' | cut -d' ' -f1`;kill $pid
If there's an easier way of doing this then please share.
To kill with grep:
kill -9 `pgrep myprocess`
more correct would be:
export pid=`ps aux | grep process_name | awk 'NR==1{print $2}' | cut -d' ' -f1`;kill -9 $pid
I normally use the killall command.
Check this link for details of this command.
I was asking myself the same question but the problem with the current answers is that they don't safe check the processes to be killed so... it could lead to terrible mistakes :)... especially if several processes matches the pattern.
As a disclaimer, I'm not a sh pro and there is certainly room for improvement.
So I wrote a little sh script :
#!/bin/sh
killables=$(ps aux | grep $1 | grep -v mykill | grep -v grep)
if [ ! "${killables}" = "" ]
then
echo "You are going to kill some process:"
echo "${killables}"
else
echo "No process with the pattern $1 found."
return
fi
echo -n "Is it ok?(Y/N)"
read input
if [ "$input" = "Y" ]
then
for pid in $(echo "${killables}" | awk '{print $2}')
do
echo killing $pid "..."
kill $pid
echo $pid killed
done
fi
kill -9 $(ps aux | grep -e myprocessname| awk '{ print $2 }')
If you run GNOME, you can use the system monitor (System->Administration->System Monitor) to kill processes as you would under Windows. KDE will have something similar.
The default kill command accepts command names as an alternative to PID. See kill (1). An often occurring trouble is that bash provides its own kill which accepts job numbers, like kill %1, but not command names. This hinders the default command. If the former functionality is more useful to you than the latter, you can disable the bash version by calling
enable -n kill
For more info see kill and enable entries in bash (1).
ps aux | grep processname | cut -d' ' -f7 | xargs kill -9 $
awk oneliner, which parses the header of ps output, so you don't need to care about column numbers (but column names). Support regex. For example, to kill all processes, which executable name (without path) contains word "firefox" try
ps -fe | awk 'NR==1{for (i=1; i<=NF; i++) {if ($i=="COMMAND") Ncmd=i; else if ($i=="PID") Npid=i} if (!Ncmd || !Npid) {print "wrong or no header" > "/dev/stderr"; exit} }$Ncmd~"/"name"$"{print "killing "$Ncmd" with PID " $Npid; system("kill "$Npid)}' name=.*firefox.*

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