Cheat Sheet

Charly's Column – cheat.sh

Article from Issue 217/2018
Author(s):

Whenever you really need documentation, it's almost always incomplete or outdated – or both. Sys admin columnist Charly K¸hnast recommends a radically different approach: the universal community documentation cheat.sh, which no Linux command and hardly any programming language should do without.

Even at school, teachers encouraged us to make cheat sheets – although actually using them was forbidden. Writing a cheat sheet helps you to keep things in mind longer. Cheat sheets are also useful after school.

For example, I have a coffee cup printed with maybe 50 important Vim commands that I occasionally consult for its more obscure finger exercises. Oddly, the matching 20-liter bucket with the basic command set for Emacs, which I saw at a Chaos Communication Congress, seems to have remained a one-off – clearly a missed opportunity.

I created an electronic cheat sheet, in which I archive code snippets and brief how-tos, in Nextcloud. Nevertheless, questions continually pop up for which I have to resort to the search engine that I mistrust the least. How do you overwrite a MAC address? How do you sort an array in Go? How do you discover the MIME encoding of a file? If only I had a cheat sheet for all of this!

Voilà: Enter cheat.sh. You can guess from where the name derives. Igor Chubin, the author, offers an online repository that provides command-line-friendly tips via HTTP(S). An example: Instead of ifconfig, which is out of fashion, Linux users should go for ip. But how does the syntax go? Just type

curl cheat.sh/ip

at the command line, and cheat.sh promptly returns the most important examples (Figure 1), including the answer to my specific question about how to overwrite a MAC address.

Figure 1: Word has got around that Linux users should use ip instead of ifconfig. But what is the command's syntax?

Multilingual

cheat.sh not only understands Linux system commands, it also provides tips for more than 60 programming languages. The requests always follow the syntax:

curl cheat.sh/<language>/<keyword>

How do you write something to a file in Ruby? Let's find out:

curl cheat.sh/ruby/write

cheat.sh's answer is impressive:

File.open(yourfile, 'w') { |file| file.write("your text") }

Imagine if I was a complete stranger to Ruby and wanted to get an overview of the language; I could do so with the command

curl cheat.sh/ruby/:learn | less

to get a compact but comprehensive introduction. In addition to the curl queries, I can use the https://cheat.sh website. Besides this, a small Bash client [1] removes the need for me to type curl. Or, I can build an alias for it. The command

curl cheat.sh/alias

explains how this works.

The Author

Charly Kühnast manages Unix systems in the data center in the Lower Rhine region of Germany. His responsibilities include ensuring the security and availability of firewalls and the DMZ.

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