Bash script checking cpu usage of specific process - bash

Question

First off, I'm new to this. I have some experience with windows scripting and apple script but not much with bash. What I'm trying to do is grab the PID and %CPU of a specific process. then compare the %CPU against a set number, and if it's higher, kill the process. I feel like I'm close, but now I'm getting the following error:
[[: 0.0: syntax error: invalid arithmetic operator (error token is ".0")
what am I doing wrong? here's my code so far:
#!/bin/bash
declare -i app_pid
declare -i app_cpu
declare -i cpu_limit
app_name="top"
cpu_limit="50"
app_pid=`ps aux | grep $app_name | grep -v grep | awk {'print $2'}`
app_cpu=`ps aux | grep $app_name | grep -v grep | awk {'print $3'}`
if [[ ! $app_cpu -gt $cpu_limit ]]; then
echo "crap"
else
echo "we're good"
fi
Obviously I'm going to replace the echos in the if/then statement but it's acting as if the statement is true regardless of what the cpu load actually is (I tested this by changing the -gt to -lt and it still echoed "crap"
Thank you for all the help. Oh, and this is on a OS X 10.7 if that is important.

Answer 1

I recommend taking a look at the facilities of ps to avoid multiple horrible things you do.
On my system (ps from procps on linux, GNU awk) I would do this:
ps -C "$app-name" -o pid=,pcpu= |
awk --assign maxcpu="$cpu_limit" '$2>maxcpu {print "crappy pid",$1}'

Answer 2

The problem is that bash can't handle decimals. You can just multiply them by 100 and work with plain integers instead:
#!/bin/bash
declare -i app_pid
declare -i app_cpu
declare -i cpu_limit
app_name="top"
cpu_limit="5000"
app_pid=`ps aux | grep $app_name | grep -v grep | awk {'print $2'}`
app_cpu=`ps aux | grep $app_name | grep -v grep | awk {'print $3*100'}`
if [[ $app_cpu -gt $cpu_limit ]]; then
echo "crap"
else
echo "we're good"
fi
Keep in mind that CPU percentage is a suboptimal measurement of application health. If you have two processes running infinite loops on a single core system, no other application of the same priority will ever go over 33%, even if they're trashing around.

Answer 3

#!/bin/sh
PROCESS="java"
PID=`pgrep $PROCESS | tail -n 1`
CPU=`top -b -p $PID -n 1 | tail -n 1 | awk '{print $9}'`
echo $CPU

Answer 4

I came up with this, using top and bc.
Use it by passing in ex: ./script apache2 50 # max 50%
If there are many PIDs matching your program argument, only one will be calculated, based on how top lists them. I could have extended the script by catching them all and avergaing the percentage or something, but this will have to do.
You can also pass in a number, ./script.sh 12345 50, which will force it to use an exact PID.
#!/bin/bash
# 1: ['command\ name' or PID number(,s)] 2: MAX_CPU_PERCENT
[[ $# -ne 2 ]] && exit 1
PID_NAMES=$1
# get all PIDS as nn,nn,nn
if [[ ! "$PID_NAMES" =~ ^[0-9,]+$ ]] ; then
PIDS=$(pgrep -d ',' -x $PID_NAMES)
else
PIDS=$PID_NAMES
fi
# echo "$PIDS $MAX_CPU"
MAX_CPU="$2"
MAX_CPU="$(echo "($MAX_CPU+0.5)/1" | bc)"
LOOP=1
while [[ $LOOP -eq 1 ]] ; do
sleep 0.3s
# Depending on your 'top' version and OS you might have
# to change head and tail line-numbers
LINE="$(top -b -d 0 -n 1 -p $PIDS | head -n 8 \
| tail -n 1 | sed -r 's/[ ]+/,/g' | \
sed -r 's/^\,|\,$//')"
# If multiple processes in $PIDS, $LINE will only match\
# the most active process
CURR_PID=$(echo "$LINE" | cut -d ',' -f 1)
# calculate cpu limits
CURR_CPU_FLOAT=$(echo "$LINE"| cut -d ',' -f 9)
CURR_CPU=$(echo "($CURR_CPU_FLOAT+0.5)/1" | bc)
echo "PID $CURR_PID: $CURR_CPU""%"
if [[ $CURR_CPU -ge $MAX_CPU ]] ; then
echo "PID $CURR_PID ($PID_NAMES) went over $MAX_CPU""%"
echo "[[ $CURR_CPU""% -ge $MAX_CPU""% ]]"
LOOP=0
break
fi
done
echo "Stopped"

Answer 5

Erik, I used a modified version of your code to create a new script that does something similar. Hope you don't mind it.
A bash script to get the CPU usage by process
usage:
nohup ./check_proc bwengine 70 &
bwegnine is the process name we want to monitor 70 is to log only when the process is using over 70% of the CPU.
Check the logs at: /var/log/check_procs.log
The output should be like:
DATE | TOTAL CPU | CPU USAGE | Process details
Example:
03/12/14 17:11 |20.99|98| ProdPROXY-ProdProxyPA.tra
03/12/14 17:11 |20.99|100| ProdPROXY-ProdProxyPA.tra
Link to the full blog:
http://felipeferreira.net/?p=1453

Answer 6

It is also useful to have app_user information available to test whether the current user has the rights to kill/modify the running process. This information can be obtained along with the needed app_pid and app_cpu by using read eliminating the need for awk or any other 3rd party parser:
read app_user app_pid tmp_cpu stuff <<< \
$( ps aux | grep "$app_name" | grep -v "grep\|defunct\|${0##*/}" )
You can then get your app_cpu * 100 with:
app_cpu=$((${tmp_cpu%.*} * 100))
Note: Including defunct and ${0##*/} in grep -v prevents against multiple processes matching $app_name.

Answer 7

I use top to check some details. It provides a few more details like CPU time.
On Linux this would be:
top -b -n 1 | grep $app_name
On Mac, with its BSD version of top:
top -l 1 | grep $app_name