$cat a.txt hello $cat b.txt killo $ls 1 a.txt b.txt l.txt trueangle u.txt $cat u.txt UPPERCASE $cat l.txt uppercase $cat a.txt >> b.txt >> l.txt >> u.txt $cat u.txt UPPERCASE hello $cat a.txt hello $cat 1 a.txt b.txt l.txt trueangle/ u.txt $cat l.txt uppercase $cat a.txt hello $cat a.txt >> b.txt $cat b.txt killo hello $cat l.txt >> u.txt $cat u.txt UPPERCASE hello uppercase $paste b.txt u.txt > final.txt $cat final.txt killo UPPERCASE hello hello uppercase $sort -t: -k1 final.txt hello hello killo UPPERCASE uppercase $