Move given directories to shared memory and create symlinks

shared_memory.sh

#!/bin/bash

for i in "$@" ; do

        if [ -h $i ] ; then
                echo "$i is a symlink";
                SYMLINKTARGET=$(readlink -f "$i")
                unlink "$i" || { echo "Error unlinking $i"; exit 1; }
                if [ -d $SYMLINKTARGET ] ; then
                        echo "Moving  $SYMLINKTARGET to $i"
                        mv $SYMLINKTARGET $i
                else
                        echo "Creating new empty directory $i"
                        mkdir "$i" || { echo "Error creating new directory $i"; exit 1; }
                fi
        fi
        if [ ! -d $i ] ; then echo "Invalid directory $i"; exit 1; fi

        NORMALIZEDDIR=`cd "$i";pwd`
        TARGETDIR=${NORMALIZEDDIR//[\/-+=.,]/_}

        if [ -d /dev/shm/$TARGETDIR ] ; then
                echo "Directory /dev/shm/$TARGETDIR already exists. Deleting it";
                rm -rf "/dev/shm/$TARGETDIR" || { echo "Error while deleting target dir /dev/shm/$TARGETDIR"; exit 1; }
        fi
        echo "Moving $i to /dev/shm/$TARGETDIR"
        mv $i /dev/shm/$TARGETDIR
        echo "Creating symlink from $i to /dev/shm/$TARGETDIR"
        ln -s /dev/shm/$TARGETDIR $i
        echo "Fixing permissions"
        chown -R vagrant:www-data /dev/shm/$TARGETDIR
        chmod -R ug+rw /dev/shm/$TARGETDIR
done

Usage: ./shared_memory.sh /var/www/magento/htdocs/var/{cache,session}

Any reason you did not move all of /var to /dev/shm? (Was /var/generated too big?)
Any reason you did not move it to /tmp? (Other than potential performance benefit?)