expand x.txt > y.txt replace TAB by spaces
nl x.txt cat with line number
uniq x.txt remove duplicates
split -l 11000 -d catalina.out salami_ split catalina.out evere 11000 lines to a file salami_nn (-d is for numeric file number)
cut -f2 tabulator.txt cut columns 2
paste x.txt y.txt merge two files by column
join -j like paste with "sql like" join on a common key
cat x.txt | tr Q P replace Q by P in x.txt
cat x.txt | tr a-z A-Z lower case to upper case
[:lower:] possible as an argument of tr