This is a long-term project to decode all of the GNU coreutils in version 8.3.

This resource is for novice programmers exploring the design of command-line utilities. It is best used as an accompaniment providing useful background while reading the source code of the utility you may be interested in. This is not a user guide -- Please see applicable man pages for instructions on using these utilities.

In order to successfully work with the Linux sed editor and the awk command in your shell scripts, you have to understand regular expressions or in short regex. Since there are many engines for regex, we will use the shell regex and see the bash power in working with regex.

First, we need to understand what regex is, then we will see how to use it.

Table of contents include:

What is regex, Types of regex, Define BRE Patterns, Special Characters, Anchor Characters, The dot Character, Character Classes, Negating Character Classes, Using Ranges, Special Character Classes, The Asterisk, Extended Regular Expressions, The question mark, The Plus Sign, Curly Braces, Pipe Symbol, Grouping Expressions, Practical examples, Counting Directory Files, Validating E-mail Address.

CLIs are a fantastic way to build products. Unlike web applications, they take a small fraction of the time to build and are much more powerful. With the web, you can do whatever the developer programmed. With CLIs, you can easily mash-up multiple tools together yourself to perform advanced tasks. They require more technical expertise to use, but still work well for admin tasks, power-user tasks, or developer products.

At Heroku, we’ve come up with a methodology called the 12 factor app. It’s a set of principles designed to make great web applications that are easy to maintain. In that spirit, here are 12 CLI factors to keep in mind when building your next CLI application. Following these principles will offer CLI UX that users will love.

We’ve also built a CLI framework called oclif that is designed to follow these principles to build great CLIs in Node.

Examples of Python and Rust code to illustrate the concept of ownership.

Very good tutorial.

Brian Kernighan

Princeton University

July 13, 2009

ranger is a console file manager with VI key bindings. It provides a minimalistic and nice curses interface with a view on the directory hierarchy. It ships with rifle, a file launcher that is good at automatically finding out which program to use for what file type.

Features

• UTF-8 Support (if your python copy supports it)
• Multi-column display
• Preview of the selected file/directory, including images
• Common file operations (create/chmod/copy/delete/...)
• Renaming multiple files at once
• VIM-like console and hotkeys
• Automatically determine file types and run them with correct programs
• Change the directory of your shell after exiting ranger
• Tabs, bookmarks, mouse support

script is an open source tool that makes a typescript of everything displayed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr.

Everything between the script and the exit command is logged to the file. This includes the confirmation messages from script itself (unless the -q flag is used). Everything between the script and the exit command is logged to the file. This includes the confirmation messages from script itself.

Recorded shell sessions can be shared using online services. The advantage of sessions recorded in this format from the usual screencasts is that shell instructions can be easily copy/pasted from the player screen.

Useful command:

script --timing=time.txt script.log

and to replay

scriptreplay --timing=time.txt script.log

See also the nice -d (divisor, speeds up playback) and -m (max delay in playback) options for replay.