Question

List the filter commands used in Linux,

Answer 1

The uniq command is filter,  this will takes its input from the sort command as well as passes output as input to uniq command;

The grep command is considered as one of most popular filter under Linux and UNIX like operating systems.

Then uniq command output is redirected to "u_sname" file. Awk, cut, Paste, grep, Sort, gzip, head, tr, uniq, perl, sed, split, tac, strings, tail, wc, tee