usage of `cat` is not helpful for reader

[flip111]

Here https://github.com/rust-embedded/book/blob/aadfc95f85e635c6a37a7b12ae9255fd39b08b36/src/intro/install/linux.md#udev-rules

Create this file in /etc/udev/rules.d with the contents shown below.

this is not referring to something the reader has already read. It's not good in english to refer to it or this before it was mentioned. Further cat /etc/udev/rules.d/70-st-link.rules should not be the contents of the file (obviously).

Suggested fix 1:

Create the file /etc/udev/rules.d/70-st-link.rules with the contents shown below.

Suggested fix 2:
Provide a command (cat + heredoc into file?) to write the file in one go

Suggested fix 3:
provide a command to open an editor

[flip111]

Similar situation here https://rust-embedded.github.io/book/start/qemu.html#a-non-standard-rust-program

[flip111]

Similar https://rust-embedded.github.io/book/start/qemu.html#running

this one is even stranger because

For convenience here's the source code of src/main.rs:

cat examples/hello.rs

Am i supposed to replace the source code of src/main.rs which was just discussed ?