Working out percentage of memory utilization

Hi there

I am middle of writing a script to allow me to see the % of the memory which is being used.

When I submit my script I don't get any errors but I just get a blank output.

Any pointers?

available=`free -m | grep available`

if [ "$available"="$new_linux_version_available" ]
then

mem_utalization=`sum=$(($mem_total/($mem_total - $mem_available) * 100))`

else
mem_buff_cache_used=`free -m  | grep ^-/+ | awk  '{print $3}'`
mem_utalization=`sum=$(((mem_buff_cache_used/($mem_buff_cache_used + $mem_buff_cache_free)) * 100))`

fi

echo $mem_utalization
echo $mem_buff_cache_used
echo $mem_buff_cache_free

[casupport@wycvlapph033 test]$ ./free_memory_script.sh



[casupport@wycvlapph033 test]$

No error message or anything comes back? All the variables work as they work in the command line

[casupport@wycvlapph033 ~]$ free -m  | grep ^-/+ | awk  '{print $3}'
7281
[casupport@wycvlapph033 ~]$ free -m  | grep ^-/+ | awk  '{print $4}'
8757
[casupport@wycvlapph033 ~]$

Cheers
Alex

Is that the entire script? On top of variables used for calculations being undefined, I see syntactical errors as well as questionable formulae yielding values > 100% for e.g. memory utilization.

Hi RudiC

Please see below the whole script

###########################################################################################
## VARIABLES
###########################################################################################
 new_linux_version_available="available"
new_linux_version_buffcache="buff/cache"
 ###########################################################################################
## Memory - TOTAL
###########################################################################################
mem_total=`free -m  | grep ^Mem | awk '{print $2}'`
 #echo $mem_total
 ###########################################################################################
## Memory - USED
###########################################################################################
mem_used=`free -m  | grep ^Mem | awk '{print $3}'`
 #echo $mem_used
 ###########################################################################################
## Memory - FREE
###########################################################################################
mem_free=`free -m  | grep ^Mem | awk '{print $4}'`
 #echo $mem_free
 ###########################################################################################
## Memory - BUFFER+CACHE
###########################################################################################
buff_cache=`free -m | grep buff/cache`
 if [ "$buff_cache"="$new_linux_version_buffcache" ]
then
 sum=`free -m  | grep ^Mem | awk '{print $6}'`
else
 mem_buffer=`free -m  | grep ^Mem | awk '{print $6}'`
mem_cache=`free -m  | grep ^Mem | awk '{print $7}'`
 sum=$(($mem_buffer + $mem_cache))
 fi
 #echo $sum
 ###########################################################################################
## Memory - AVAILABLE
###########################################################################################
available=`free -m | grep available`
 if [ "$available"="$new_linux_version_available" ]
then
 mem_available=`free -m  | grep ^Mem | awk '{print $7}'`
else
mem_buff_cache_free=`free -m  | grep ^-/+ | awk  '{print $4}'`
mem_available=`sum=$(($mem_buff_cache_free + $mem_free))`
 fi
 #echo $mem_available
###########################################################################################
## Memory - UTILIZATION
###########################################################################################
available=`free -m | grep available`
 if [ "$available"="$new_linux_version_available" ]
then
 mem_utalization=`sum=$(($mem_total/($mem_total - $mem_available) * 100))`
 else
mem_buff_cache_used=`free -m  | grep ^-/+ | awk  '{print $3}'`
mem_utalization=`sum=$(((mem_buff_cache_used/($mem_buff_cache_used + $mem_buff_cache_free)) * 100))`
 fi
 echo $mem_utalization
echo $mem_buff_cache_used
echo $mem_buff_cache_free

Have you been able to identify the syntactical errors and the senseless formulae?

EDIT: I have to correct myself - those are not syntactical erors, but semantical / logical ones.

Hi RudiC

I have only been able to spot one,

There should have been a $ infront of the mem_buff

In principle, yes. However, inside the ((...)) ("arithmetic expansion") you don't need the $ , see e.g. man bash .

But, you have picked the perfect line to illustrate what I was talking about:
To produce a value to be assigned to mem_utalization , you use (the deprecated `...` version of) "command substitution" which is the standard output of the command. Your command is a variable assignment ( sum=... ). What is the stdout of a variable assignment? Nothing! So, mem_utalization is empty.
The next one is $mem_total/($mem_total - $mem_available) which will result in a value above 100% given all values used are positive. Is that what you want?

In your above script you're running free , grep , and awk umpteen times, each causing a (costly) process creation - why not do it all in a single pass? Try

free | awk '/^Mem/ {print "Total:", $2, ", free:", $4, ", used:", $3, ", something:", ($2-$7)/$2*100, "%"}' OFMT="%.2f"
Total: 1918976 , free: 100452 , used: 955060 , something: 63.88 %

without assessing your interpretation of free 's numbers / columns. You can even have the distinction between various linux versions done in that one small awk script ...

Hi RudiC

Thank you for your reply and your help with this.

Just a quick question regarding the final part of this code:

($2-$7)/$2*100, "%"}' OFMT="%.2f"

($2 - $7) are we taking the second variable away from the seventh?

And the final part I don't quite understand is that two decimal places?

Cheers

We are subtracting field 7 ("available") from field 2 ("total"), as you do in your script above.
The OFMT is an awk variable defining the "format for printing numbers; initially = "%.6g"." ( man awk ), and yes, we use it for the percentage output.