A Script to Clear Cached RAM on Linux

clearRAM.sh

#!/bin/bash
## Bash Script to clear cached memory on (Ubuntu/Debian) Linux
## By Philipp Klaus
## see <http://blog.philippklaus.de/2011/02/clear-cached-memory-on-ubuntu/>

if [ "$(whoami)" != "root" ]
then
  echo "You have to run this script as Superuser!"
  exit 1
fi

# Get Memory Information
freemem_before=$(cat /proc/meminfo | grep MemFree | tr -s ' ' | cut -d ' ' -f2) && freemem_before=$(echo "$freemem_before/1024.0" | bc)
cachedmem_before=$(cat /proc/meminfo | grep "^Cached" | tr -s ' ' | cut -d ' ' -f2) && cachedmem_before=$(echo "$cachedmem_before/1024.0" | bc)

# Output Information
echo -e "This script will clear cached memory and free up your ram.\n\nAt the moment you have $cachedmem_before MiB cached and $freemem_before MiB free memory."

# Test sync
if [ "$?" != "0" ]
then
  echo "Something went wrong, It's impossible to sync the filesystem."
  exit 1
fi

# Clear Filesystem Buffer using "sync" and Clear Caches
sync && echo 3 > /proc/sys/vm/drop_caches

freemem_after=$(cat /proc/meminfo | grep MemFree | tr -s ' ' | cut -d ' ' -f2) && freemem_after=$(echo "$freemem_after/1024.0" | bc)

# Output Summary
echo -e "This freed $(echo "$freemem_after - $freemem_before" | bc) MiB, so now you have $freemem_after MiB of free RAM."

exit 0

Newbie to UNIX.

Thanks a Lot !!!

wow,

We need to have bc installed to run the script
sudo apt install bc

Thanks a lot...!!

hello!
i copy-pasted your script to a file (named flushram.sh) then i chmodded it to 777, but when i run it i get this output and cache were not cleared :(
any clues?

root@raspberrypi:/home# sudo sh flushram.sh
flushram.sh: 13: flushram.sh: bc: not found
flushram.sh: 14: flushram.sh: bc: not found
This script will clear cached memory and free up your ram.

At the moment you have  MiB cached and  MiB free memory.
flushram.sh: 29: flushram.sh: bc: not found
flushram.sh: 32: flushram.sh: bc: not found
This freed  MiB, so now you have  MiB of free RAM.
root@raspberrypi:/home#

Many thanks for any help
Juri

hello!
i copy-pasted your script to a file (named flushram.sh) then i chmodded it to 777, but when i run it i get this output and cache were not cleared :(
any clues?

root@raspberrypi:/home# sudo sh flushram.sh
flushram.sh: 13: flushram.sh: bc: not found
flushram.sh: 14: flushram.sh: bc: not found
This script will clear cached memory and free up your ram.

At the moment you have  MiB cached and  MiB free memory.
flushram.sh: 29: flushram.sh: bc: not found
flushram.sh: 32: flushram.sh: bc: not found
This freed  MiB, so now you have  MiB of free RAM.
root@raspberrypi:/home#

Many thanks for any help
Juri

You need to install "bc" to run this script.
The “bc” is the command-line calculator for Linux. You can simply do calculations through your command-line.
If your OS is Redhat/Centos use >>> "yum install bc"
or Ubuntu >> "apt-get install bc"

Permission denied

Works like a charm, thanks.

Just make sure to install bc !!

sudo apt-get install bc

then run script as follows:

sudo ./flushram.sh

My result:

At the moment you have 223 MiB cached and 2425 MiB free memory.
This freed 63 MiB, so now you have 2488 MiB of free RAM.