#! /bin/bash
# rect-area.sh : a script to find area of rectangle
echo -n "Enter width: "
read width
echo -n "Enter height: "
read height
area=`expr $width '*' $height`
echo "Area of rectangle=${width}x${height}=$area"

#! /bin/bash
# rect-area.sh : a script to find area of rectangle
echo -n "Enter width: "
read width
echo -n "Enter height: "
read height
area=`expr $width '*' $height`
echo "Area of rectangle=${width}x${height}=$area" >> m.txt

sed -e 's/$x/$y/g' m.txt

x=1
y=2

echo "please Insert New X Value"
read $x
echo "please Insert New Y Value"
read $y
sed 's/1/$x/' > m.txt
sed 's/2/$y/' > m.txt
echo "Done !"

echo "Please Enter New X"
read $x
echo "Please Enter New Y"
read $y
sed -e 's/1/$x/' m.txt > text.txt
sed -e 's/2/$y/' text.txt >m.txt
rm -f text.txt
echo "Done ! "

[root@box ~]# cat m.txt
x=$x
y=$y

echo "Please Enter New X"
read $x
echo "Please Enter New Y"
read $y
#sed -e 's/1/$x/' m.txt > text.txt
#sed -e 's/2/$y/' text.txt >m.txt
#rm -f text.txt
sed '/x=/s'/\[0-9\]/$x/g'
sed '/y=/s'/\[0-9\]/$y/g'
echo "Done ! "

Please Enter New X
44
Please Enter New Y
55
sed: -e expression #1, char 37: unterminated `s' command
Done !

sed '/x=/ s/\[a-z-0-9\]/$x/g'