Table of Contents

Find Memory Usage

System memory used and free

Total Used and Free Memory in MBytes (in that order) 

free -m|grep "buffers/cache"|cut -d":" -f2

Memory by Process

Raw 

ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS

Human readable 

ps -e -orss=,args= | sort -b -k1,1n | awk '{ split( "KB MB GB" , v ); s=1; while( $1>1024 ){ $1/=1024; s++ } print int($1) " " v[s] " " $2 }'

Memory by Process - Grouped together

Raw 

ps -e -orss=,args= | awk '{arr[$2]+=$1} END {for (i in arr) {print arr[i],i}}' | sort -b -k1,1n

Human readable 

ps -e -orss=,args= | awk '{arr[$2]+=$1} END {for (i in arr) {print arr[i],i}}' | sort -b -k1,1n | awk '{ split( "KB MB GB" , v ); s=1; while( $1>1024 ){ $1/=1024; s++ } print int($1) " " v[s] " " $2 }'

Total RSS Memory

ps -e -orss= | awk '{ sum += $1 } END { print sum }'

Human redable 

ps -e -orss= | awk '{ sum += $1 } END { print sum }' | awk '{ split( "KB MB GB" , v ); s=1; while( $1>1024 ){ $1/=1024; s++ } print int($1) " " v[s] " " $2 }'

Total Memory

smem -w -t -k

Use lshw - for listing hardware including physical memory slots