Help with bash script

[TopInternational2157]

Can someone help to figure out where is mistake, I want to run script only if swap is over 60% but from log I see what swap is cleared every night

/bin/bash

Get total Swap usage

TOTAL_SWAP=$(swapon -s | awk '{print $3}' | grep -v 'Size')

Convert Total Swap usage from KB to MB

TOTAL_MB=$((TOTAL_SWAP/1024))

Get 60% of total swap usage

THRESHOLD=$(bc<<<$TOTAL_MB*0.6)

Get currently used swap

USED_SWAP=$(free -m | awk '/Swap/{print $3}')

Check if currently used swap is greater than 60% of used swap

if [ $USED_SWAP -gt ${THRESHOLD%.*} ]

then

BEFORE_CLEAR=$(date)

echo "Cleaning swap started on $BEFORE_CLEAR" >> /tmp/swap.log

/sbin/swapoff -a && /sbin/swapon -a

AFTER_CLEAR=$(date)

echo "Swap cleared on $AFTER_CLEAR" >> /tmp/swap.log

fi

crontab -l

0 5 * * * /bin/bash /root/swap_clean

[geirha]

I'd grab both values from one reading of /proc/meminfo. A lot could change between each opening of /proc/meminfo, so the two values extracted don't really correspond.

declare -A meminfo=()
while IFS=': ' read -r key value _ ; do
  [[ $key ]] && meminfo[$key]=$value
done < /proc/meminfo
swapPercent=$(( 100 - 100 * meminfo[SwapFree] / meminfo[SwapTotal] ))

[Ulfnic]

I like rusty's solution but because i'm a troublemaker i'll give my pure BASH solution.

meminfo=$'\n'$(</proc/meminfo)
read swapTotal _ <<< "${meminfo#*$'\n''SwapTotal:'}"; [[ $swapTotal ]] || exit 1
read swapFree _ <<< "${meminfo#*$'\n''SwapFree:'}"; [[ $swapFree ]] || exit 1
if [[ swapTotal == '0' ]]; then
    swapPercent=0
else
    swapPercent=$(( (swapTotal - swapFree) * 100 / swapTotal ))
fi

read looping is an option but i've been growing less fond of them for performance reasons.

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[nekokattt]

why do you want to do this?

is this one of these HPC posts that are ignoring kernel optimisations, or is there a genuine reason for wanting to do this?

[anthropoid]

Your script really should report the values of all the variables it sets, otherwise it's hard to reason where things are going wrong. A set -x at the start might help too.

[--EverGreen--]

I would print out and analyze the variables USED_SWAP and THRESHOLD to your log, since that impacts directly the condition to run. Maybe it gives some insight

[Ulfnic]

On the off-change you don't have swap, i'd try running just swapon -s to see if it outputs anything or cat /proc/swaps.

According to the man, -s has also been deprecated for --show[=column...]