Shell Programming and Scripting

$dpdir= DB_FROM_$from_TO_$to
mkdir $dpdir

dpdir=DB_FROM_${from}_TO_${to}

./datapump.sh: line 57: =DP_FROM_{ad}_TO_{af}: command not found

# good
var=value

# bad
var =value
var= value

##############################################
read -p "Enter From Region: " from
echo "From Region is : $from"
if [ `echo $from` = `echo $from | tr [:upper:] [:lower:]` ];then
    froml=$(case_convert $from)
    echo "After Case Convert : $froml"
else
    froml=$from
    echo "After Case Convert : $froml"
fi

read -p "Enter To Region: " to
echo "To Region is : $to"
if [ `echo $to` = `echo $to | tr [:upper:] [:lower:]` ];then
        tol=$(case_convert $to)
        echo "After Case Convert : $tol"
else
        tol=$to
        echo "After Case Convert : $tol"
fi

read -p "Enter From TNS: " ftns
echo "From TNS is : $ftns"

read -p "Enter To TNS: " ttns
echo "To TNS is : $ttns"

read -p "Enter From Pwd: " fpwd
echo "From User Pwd is : $fpwd"

read -p "Enter To Pwd: " tpwd
echo "To User Pwd is : " $tpwd

read -p "Enter Apps Pwd: " $apwd
echo "Apps Pwd is : " $apwd

###############################################

###############################################
Create Directories and Sub-Directories
###############################################

$dpdir=DP_FROM_{$from}_TO_{$to}
mkdir $dpdir

$dpdir=DP_FROM_{$from}_TO_{$to}

dpdir=DP_FROM_${from}_TO_${to}

to=$(echo $to | tr '[a-z]' '[A-Z]')
from=$(echo $from | tr '[a-z]' '[A-Z]')

if [ `echo $from` = `echo $from | tr [:upper:] [:lower:]` ];then
...

DP_FROM_{AF}_TO_{AD}