1.sh

cat file1.txt file2.txt file3.txt > merged.txt # Combine the 3 files into one
sort merged.txt > combined.txt                 # Sort the different lines
head -n 2 combined.txt                         # Show the first 2 lines to stdout
# Onliner:
# cat file1.txt file2.txt file3.txt | sort | tee combined.txt | head -n 2

2.sh

tr '[:lower:]' '[:upper:]' < file1.txt | sort -r | uniq
# Lowercase to Uppercase
#                          < File input
#                                        Sort in reverse order
#                                                  Remove duplicates