Show N biggest directories in linux bash

du (disk usage) utility in linux bash summarizes disk usage of each directory or file. By default, it outputs only directories. Just enter some dir and type

$ du ./

Toggling string case in linux bash

It’s quite an academic task, but anyway useful sometimes. I’ve collected different ways to do it in terminal in linux. Some of them work with UTF-8 characters (some it will toggle case for “й”, “ё” and so on. It will not in general handle special ligatures, such as “ß”” and “fi”.)

Ways are: sed, perl, python, awk, tr, bash, dd.

AWK: a powerful tool for programmer

Introduction

AWK is an acronym of first letters of its authors (Aho, Weinberger and Kernighan). It is a data-manipulating scripting language with huge possibilities. There are several implementations of it: awk is a canonical one, nawk (new awk), mawk (default in Ubuntu 12.04), gawk is GNU awk. I recommend latter one, because it works correct with unicode symbols in example:

$ echo юникод | gawk "{res = toupper(\$1); print res;}"
ЮНИКОД