The terminal

At the bottom of every page, just above the footer, sits a small terminal with an input line. It is not a real Linux, it is a piece of JavaScript that rebuilds a few commands the way you know them from a shell. You cannot break anything with it. It only shows from tablet width up, there is no terminal on a phone.

Using it

Click the input line, or press / or Ctrl+K anywhere on the page, and the cursor is in it. Type a command and press Enter. The output unfolds above the line, and Esc folds it away again.

help lists every command. The up and down arrow keys bring back earlier input, and Tab completes a command or page name you have started typing.

In the examples below the command has a $ in front of it. You do not type it, it only marks what is input. What follows below it is the output.

cat

cat is short for concatenate and prints the contents of files. Here the pages of the site are the files, and cat shows a page’s short description. ls lists what there is.

$ cat projects
Overview of past and current projects.

Without a name but with a pipe in front of it (see below), cat simply passes on whatever comes in.

curl

A real curl sends an HTTP request to an address and prints the response, with -I only the headers. A browser will not let a page do that for any address it likes, so curl here opens a public address in a new tab. That can be a full URL or a path on this site.

$ curl /en/projects/
--> https://www.dirnhofer.net/en/projects/  (new tab)

wget does the same.

base64

Base64 writes any bytes using only 64 characters: upper and lower case letters, digits, + and /. That way binary data survives any channel that only knows text, an email for instance. Nothing is encrypted, anyone can turn it back. There are often one or two = at the end, which are only padding.

Without an option, base64 encodes the text after it:

$ base64 hallo
aGFsbG8=

With -d it decodes it again:

$ base64 -d aGFsbG8=
hallo

Pipes

A | between two commands sends the output of the first into the second as input. echo prints whatever follows it, and together with a pipe that is the usual way to decode something:

$ echo aGFsbG8= | base64 -d
hallo

It also works over several stages in a row, and other commands such as grep or sort read what comes out of a pipe as well.