Simple script to fill RAM for testing purposes

fill_ram.sh

#!/bin/sh

# Script to fill RAM memory with writing zeroes to /dev/shm.
# Usage:
#   ./fill_ram.sh <STEP> <THRESHOLD>
#       <STEP>: filling step (%)
#       <THRESHOLD>: used memory threshold (%)
# Example:
#   ./fill_ram.sh 5 70
#   Fill RAM with 5% step and stop filling on 70% memory used.

# Default memory step in percents
DEFAULT_STEP_PCT=10
# Default memory treshold in percents
DEFAULT_THRESHOLD_PCT=100

# Total memory
TOTAL_MEM=$(free --mega | grep -oP '\d+' | head -n 1)
# Memory step in percents
MEM_STEP_PCT="${1:-$DEFAULT_STEP_PCT}"
# Memory step in MB
MEM_STEP=$(expr $TOTAL_MEM \* $MEM_STEP_PCT / 100)
# Memory treshold in percents
MEM_THRESHOLD_PCT="${2:-$DEFAULT_THRESHOLD_PCT}"
# Memory treshold in MB
MEM_THRESHOLD="$(expr $TOTAL_MEM \* $MEM_THRESHOLD_PCT / 100)"

# Used memory
get_used_mem(){
    shared=$(free --mega --total | grep -oP '\d+' | head -4 | tail -1)
    used=$(free --mega --total | grep -oP '\d+' | tail -2 | head -1)
    expr $shared + $used
}

# Keyboard interrupt handler
ctrl_c() {
    rm -rf /dev/shm/fill_*
    echo "Memory cleaned."
    exit
}
trap ctrl_c INT

echo -n "Total memory: $TOTAL_MEM MB. "
echo -n "Used memory: $(get_used_mem) MB. "
echo -n "Memory filling step: $MEM_STEP MB ($MEM_STEP_PCT%). "
echo -n "Threshold: $MEM_THRESHOLD MB ($MEM_THRESHOLD_PCT%). "
echo -n "Hit Ctrl+C to stop.\n"
sleep 3

range=$(expr $TOTAL_MEM / $MEM_STEP)
for i in $(seq $range); do
    if [ $(get_used_mem) -ge $MEM_THRESHOLD ]; then
        echo "Threshold reached. Hit Ctrl+C to clean memory."
        sleep infinity
    fi
    dd if=/dev/zero of=/dev/shm/fill_$i bs=1M count=$MEM_STEP status=none
    echo "Written $MEM_STEP MB to /dev/shm/fill_$i. Used: $(get_used_mem) MB."
    sleep 1
done