Shell Script to Check Memory (RAM) Usage

In this tutorial, I will show a shell script to check memory usage for each program or application on Linux. The script outputs shared and private memory for each program running in Linux. Since memory calculation is bit complex, this shell script tries best to find more accurate results.

This script use 2 files ie '/proc/../status' (to get the name of the process) and '/proc/../smaps' for memory statistic of process. Then the script will convert all data into Kb, Mb, Gb. Also, make sure you install bc command.

You can download linux memory usage script in pdf version and the script is also available in Github.

Shell Script to Check Memory Usage

Check the following script which calculates memory usage and print outputs.

#!/bin/bash
# Make sure only root can run our script

if [ "$(id -u)" != "0" ]; then
echo "This script must be run as root" 1>&2
exit 1
fi

### Functions
#This function will count memory statistic for passed PID
get_process_mem ()
{
PID=$1
#we need to check if 2 files exist
if [ -f /proc/$PID/status ];
then
if [ -f /proc/$PID/smaps ];
then
#here we count memory usage, Pss, Private and Shared = Pss-Private
Pss=`cat /proc/$PID/smaps | grep -e "^Pss:" | awk '{print $2}'| paste -sd+ | bc `
Private=`cat /proc/$PID/smaps | grep -e "^Private" | awk '{print $2}'| paste -sd+ | bc `
#we need to be sure that we count Pss and Private memory, to avoid errors
if [ x"$Rss" != "x" -o x"$Private" != "x" ];
then

let Shared=${Pss}-${Private}
Name=`cat /proc/$PID/status | grep -e "^Name:" |cut -d':' -f2`
#we keep all results in bytes
let Shared=${Shared}*1024
let Private=${Private}*1024
let Sum=${Shared}+${Private}

echo -e "$Private + $Shared = $Sum \t $Name"
fi
fi
fi
}

#this function make conversion from bytes to Kb or Mb or Gb
convert()
{
value=$1
power=0
#if value 0, we make it like 0.00
if [ "$value" = "0" ];
then
value="0.00"
fi

#We make conversion till value bigger than 1024, and if yes we divide by 1024
while [ $(echo "${value} > 1024"|bc) -eq 1 ]
do
value=$(echo "scale=2;${value}/1024" |bc)
let power=$power+1
done

#this part get b,kb,mb or gb according to number of divisions
case $power in
0) reg=b;;
1) reg=kb;;
2) reg=mb;;
3) reg=gb;;
esac

echo -n "${value} ${reg} "
}

#to ensure that temp files not exist
[[ -f /tmp/res ]] && rm -f /tmp/res
[[ -f /tmp/res2 ]] && rm -f /tmp/res2
[[ -f /tmp/res3 ]] && rm -f /tmp/res3

#if argument passed script will show statistic only for that pid, of not – we list all processes in /proc/ #and get statistic for all of them, all result we store in file /tmp/res
if [ $# -eq 0 ]
then
pids=`ls /proc | grep -e [0-9] | grep -v [A-Za-z] `
for i in $pids
do
get_process_mem $i >> /tmp/res
done
else
get_process_mem $1>> /tmp/res
fi

#This will sort result by memory usage
cat /tmp/res | sort -gr -k 5 > /tmp/res2

#this part will get uniq names from process list, and we will add all lines with same process list
#we will count nomber of processes with same name, so if more that 1 process where will be
# process(2) in output
for Name in `cat /tmp/res2 | awk '{print $6}' | sort | uniq`
do
count=`cat /tmp/res2 | awk -v src=$Name '{if ($6==src) {print $6}}'|wc -l| awk '{print $1}'`
if [ $count = "1" ];
then
count=""
else
count="(${count})"
fi

VmSizeKB=`cat /tmp/res2 | awk -v src=$Name '{if ($6==src) {print $1}}' | paste -sd+ | bc`
VmRssKB=`cat /tmp/res2 | awk -v src=$Name '{if ($6==src) {print $3}}' | paste -sd+ | bc`
total=`cat /tmp/res2 | awk '{print $5}' | paste -sd+ | bc`
Sum=`echo "${VmRssKB}+${VmSizeKB}"|bc`
#all result stored in /tmp/res3 file
echo -e "$VmSizeKB + $VmRssKB = $Sum \t ${Name}${count}" >>/tmp/res3
done

#this make sort once more.
cat /tmp/res3 | sort -gr -k 5 | uniq > /tmp/res

#now we print result , first header
echo -e "Private \t + \t Shared \t = \t RAM used \t Program"
#after we read line by line of temp file
while read line
do
echo $line | while read a b c d e f
do
#we print all processes if Ram used if not 0
if [ $e != "0" ]; then
#here we use function that make conversion
echo -en "`convert $a` \t $b \t `convert $c` \t $d \t `convert $e` \t $f"
echo ""
fi
done
done < /tmp/res

#this part print footer, with counted Ram usage
echo "--------------------------------------------------------"
echo -e "\t\t\t\t\t\t `convert $total`"
echo "========================================================"

# we clean temporary file
[[ -f /tmp/res ]] && rm -f /tmp/res
[[ -f /tmp/res2 ]] && rm -f /tmp/res2
[[ -f /tmp/res3 ]] && rm -f /tmp/res3

Shell Script Output

I have named this script as 'memstat.sh' and find the output by running the script as follows:

[root@centos-cluster-node1 ~]# ./memstat.sh
Private + Shared = RAM used Program
36.26 mb + 268.00 kb = 36.52 mb python
20.49 mb + 238.00 kb = 20.72 mb iscsiuio
4.78 mb + 451.00 kb = 5.22 mb rgmanager(2)
3.62 mb + 283.00 kb = 3.90 mb NetworkManager
2.53 mb + 1.36 mb = 3.89 mb sshd(3)
2.30 mb + 355.00 kb = 2.64 mb multipathd
2.25 mb + 176.00 kb = 2.42 mb hald
1.69 mb + 298.00 kb = 1.98 mb iscsid(2)
1.45 mb + 432.00 kb = 1.87 mb dhclient(3)
1.62 mb + 161.00 kb = 1.77 mb cupsd
704.00 kb + 819.00 kb = 1.48 mb udevd(3)
856.00 kb + 554.00 kb = 1.37 mb bash(2)
1.00 mb + 314.00 kb = 1.31 mb qmgr
984.00 kb + 314.00 kb = 1.26 mb pickup
976.00 kb + 316.00 kb = 1.26 mb master
1.07 mb + 21.00 kb = 1.09 mb rsyslogd
804.00 kb + 240.00 kb = 1.01 mb modem-manager
904.00 kb + 40.00 kb = 944.00 kb pcscd
804.00 kb + 33.00 kb = 837.00 kb ricci
788.00 kb + 38.00 kb = 826.00 kb dbus-daemon
660.00 kb + 32.00 kb = 692.00 kb crond
536.00 kb + 69.00 kb = 605.00 kb rpc.statd
528.00 kb + 46.00 kb = 574.00 kb init
216.00 kb + 357.00 kb = 573.00 kb saslauthd(5)
544.00 kb + 21.00 kb = 565.00 kb wpa_supplicant
484.00 kb + 72.00 kb = 556.00 kb mingetty(6)
316.00 kb + 58.00 kb = 374.00 kb rpcbind
116.00 kb + 237.00 kb = 353.00 kb memstat.sh
328.00 kb + 13.00 kb = 341.00 kb auditd
248.00 kb + 84.00 kb = 332.00 kb hald-runner
312.00 kb + 8.00 kb = 320.00 kb oddjobd
216.00 kb + 81.00 kb = 297.00 kb hald-addon-stor
196.00 kb + 88.00 kb = 284.00 kb hald-addon-inpu
272.00 kb + 4.00 kb = 276.00 kb rpc.idmapd
176.00 kb + 52.00 kb = 228.00 kb hald-addon-acpi
--------------------------------------------------------
98.57 mb
========================================================
[root@centos-cluster-node1 ~]#

Read Also: Shell Script to Check Linux Server Health

Bobbin Zachariah 8:52 pm

Comments

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2 Comments

  1. Thank you for your information. I am trying to test the script and executed in my board. But i got very few memory usage with the above script. As free -m and meminfo is showing 70MB used but the script is showing 19.83 B. Private + Shared = Ram usage. Do we need change anything in the script to get map between : free -m and meminfo to this script. Please help me in this.