Regular Linux

 Matching -Xms3G -Xmx20GB

./jvm.sh "-Xmx300G"
 

cat jvm.sh 
echo $1
in=$1
regularExp="^([\s]*-Xm[xs][0-9]*[KBMGTkbmgt][Bb]?[\s]*){1,2}$"
if [[ $in =~ $regularExp ]] ; then
 echo "match"
else
 echo "no match"
fi