Linux Shell Scripting: Lowercase n Uppercase

Q: Write a shell script for manipulating the case of input text.

Source Code

#!/bin/bash
while true
do
echo "Enter your choice"
echo -e "1.print file in lower case \t2.print file in upper case \t3.string to lower case \t\n4.string to upper case \t\t5.Invert case of input string \t6.exit"
read choice
case $choice in
1)
echo "Files in the current folder are as follows"
ls 
echo "Enter the file name to be printed in lower case:"
read f1
echo "Actual contents of file "
cat $f1
tr '[A-Z]' '[a-z]' <$f1
echo "Operation Successful"  ;;
2)
echo "Files in the current folder are as follows"
ls  
echo "Enter the file name to be printed in upper case:"
read f2
echo "Contents before conversion"
cat $f2
tr '[a-z]' '[A-Z]'  <$f2
echo "Operation successful"  
;;
3)
echo "Enter the string to be converted:"
read str
ans=${str,,}
echo "String in lower case is: "$ans  ;;
4)
echo "Enter the string to be converted:"
read str
ans=${str^^}
echo "String in uppercase is: " $ans  ;;
5)
echo "Enter the string to be inverted"
read str
ans=${str~~}
echo "Inverted string is :" $ans  ;;
6)exit  ;;
esac
done

Output

[student@localhost loweruppercase]$ sh grpb7.sh
Enter your choice
1.print file in lower case     2.print file in upper case     3.string to lower case    
4.string to upper case         5.Invert case of input string     6.exit
1
Files in the current folder are as follows
grpb7.sh  grpb7.sh~  sample
Enter the file name to be printed in lower case:
sample
Actual contents of file
ThiS i$ a SaMPle FiLe f0r te$tinG tHE ProGr@m
this i$ a sample file f0r te$ting the progr@m
Operation Successful
Enter your choice
1.print file in lower case     2.print file in upper case     3.string to lower case    
4.string to upper case         5.Invert case of input string     6.exit
2
Files in the current folder are as follows
grpb7.sh  grpb7.sh~  sample
Enter the file name to be printed in upper case:
sample
Contents before conversion
ThiS i$ a SaMPle FiLe f0r te$tinG tHE ProGr@m
THIS I$ A SAMPLE FILE F0R TE$TING THE PROGR@M
Operation successful
Enter your choice
1.print file in lower case     2.print file in upper case     3.string to lower case    
4.string to upper case         5.Invert case of input string     6.exit
3
Enter the string to be converted:
SaMpLE
String in lower case is: sample
Enter your choice
1.print file in lower case     2.print file in upper case     3.string to lower case    
4.string to upper case         5.Invert case of input string     6.exit
4
Enter the string to be converted:
Te$t
String in uppercase is:  TE$T
Enter your choice
1.print file in lower case     2.print file in upper case     3.string to lower case    
4.string to upper case         5.Invert case of input string     6.exit
5
Enter the string to be inverted
InvERT !t
Inverted string is : iNVert !T
Enter your choice
1.print file in lower case     2.print file in upper case     3.string to lower case    
4.string to upper case         5.Invert case of input string     6.exit
6

07:31