Find and Kill Process – How to Find the ID of a Process and Kill It

grepkillprocessps

When ever I need to kill a background process I do ps -e | grep <process_name>

Which prints something like this 1766 ? 00:00:13 conky , Then I use the process ID to kill it like so kill 1766 .

Is there any way I can simplify this ? Make it quicker ? reduce the amount of typing ?

Best Answer

(TL,DR: pgrep, pkill)

Many unix variants come with the pgrep and its companion pkill: Solaris, Linux (part of the standard process utilities, may be absent from embedded Linux systems), FreeBSD, OpenBSD, NetBSD, … but only from MacPorts on OS X, not AIX, and only recently in HP-UX. The pgrep utility shows the process ID of processes matched by name, user and a few other criteria. The argument to pgrep is interpreted as a regexp that must match part of the process's executable's name (unless you pass an option to change this). If you call pkill instead of pgrep, the utility sends a signal instead of displaying the process IDs.

Another similar utility is pidof. On Linux, it's provided by SysVinit or BusyBox (so you'll often find it on an embedded Linux system that doesn't have pgrep); there are also ports on other unix variants. The pidof utility has fewer options, it mostly only matches whole executable file names. Its companion utility killall sends a signal to the matched programs¹.

¹ _{Beware that killall has a different meaning on Solaris and possibly other unix variants; do not type killall as root on Solaris.}

killall

I have a recurring issue with Chrome where it eventually needs to be dealt with by killing it. I usually do this command to eradicate all of them.

$ killall chrome

pgrep & pkill

But I could do this as well, to deal with only the newest process:

# to list
$ pgrep -n chrome
23108

# to kill
$ pkill -n chrome

Killing based on your command line

You can also add the -f switch to reach those processes that have long path arguments that you'd rather match on, instead of just their executable's name.

For example, say I had these processes:

$ ps -eaf | grep some
saml     26624 26575  0 22:51 pts/44   00:00:00 some weird command
saml     26673 26624  0 22:51 pts/44   00:00:00 some weird command's friend
saml     26911 26673  8 22:54 pts/44   00:00:00 some weird command's friend

They're just Bash shells with their ARGV0 set to those names. Incidentally I made those processes using this trick:

$ (exec -a "some weird command name's friend" bash)

Going after friends

But say I have a lot of them, and I only want to go after a particular set of them because they have "friend" in their command lines. I could do this:

$ pgrep -f friend
26673
26911

Going after the youngest friend

And if there were a couple of them and I wanted to go after the newest, add the -n switch back into the mix:

$ pgrep -fn friend
26911

You can also use regular expressions when enlisting the -f switch, so these would work, for example:

$ pgrep -f "weird.*friend"
26673
26911

Displaying their names

You can double check the processes names using the -l switch:

$ pgrep -f "weird.*friend" -l
26673 some weird command's friend
26911 some weird command's friend

Controlling the output

Or tell pgrep to list the process IDs delimited using a comma (,):

$ pgrep -f "weird.*friend" -d,
26673,26911

You can do cool things like this:

$ ps -fp $(pgrep -f weird -d,)
UID        PID  PPID  C STIME TTY          TIME CMD
saml     26624 26575  0 22:51 pts/44   00:00:00 some weird command
saml     26673 26624  0 22:51 pts/44   00:00:00 some weird command's friend
saml     26911 26673  0 22:54 pts/44   00:00:00 some weird command's friend

So how do I kill the high CPU process?

I would use the above to be more selective in going after a high CPU process. You could use the approach of killing using these methods:

# newest guys
$ pkill -nf vlc ; pkill -nf opensnap

# kill all of these
$ killall vlc; killall opensnap

Look at their CPU loads:

$ top -b -n 1 | grep -E $(pgrep -f "weird.*friend" -d\|) | grep -v grep
26911  0.1  112m 106m 6408  848 4900 1512    0    0 S  20   0  0.0 some weird command's friend                                     
26673  0.1  112m 106m 6392  848 5020 1504    0    0 S  20   0  0.0 some weird command's friend

Here I've changed the delimiter from a comma (,) aka. this switch -d,, to a pipe (|) aka. this switch -d\|, so that I can use it in a grep. Doing this will return the process IDs like this:

$ pgrep -f "weird.*friend" -d\|
26673|26911

We then insert these into the grep -E ... command so we can filter the output from top based on certain process IDs.

This might seem like a lot of bending backwards, but we now know with certainty that the process IDs we're using are only the ones related to a give process named "weird.*friend".

From here you can find the process with the highest CPU and kill it, if you really want to go that way.

A more targeted approach to high CPU

$ top -b -n 1 | grep -E $(pgrep -f "weird.*friend" -d\|) | \
    grep -v grep | sort -nk14,14 | tail -1
26911  0.1  112m 106m 6408  848 4900 1512    0    0 S  20   0  0.0 some weird command's friend

The above shows the sorted output from top by the CPU column (14th). It's sorted from lowest to highest, so we take the last line (tail -1) which would be the highest CPU process of the "weird.*friend" processes.