Userland talk for W&M ACM

userland_talk.md

UNIX: userland and the shell

• GUI file managers are built on top of coreutils (GNU/BSD)
• you can just run the coreutils directly in a shell
  • reads command and spits out the result
  • matrix of monospaced text
• syntax: binary space arg1 space arg2 space ...

exercises

Run in a terminal next to a Finder window in the same directory to see results:

touch filename
ls
cp
mv
rm
ln -s
mkdir filename
cd
pwd

But the shell does more flexible things too!

cat filename
echo "text"

more theory

• every command can take an arbitrary amount of text as input (stdin) and spit output on stdout
• by default:
  • stdin is empty
  • stdout is connected to the terminal
• you can take the contents of files as input: "taking a file as stdin"
• you can put the output of a command into a file: "redirecting stdout to file"
• you can feed the output of a command and feed it as input to another: "piping"
• stderr is like stdout but usually connected to a terminal in case something goes wrong

more exercises

echo "hello" > hello.txt
echo "world" >> hello.txt

echo "angry message" | tr a-z A-Z
echo "NICE MESSAGE" | tr A-Z a-z
echo "angry message" | tr a-z A-Z > email.txt
rm email.txt

tr a-z A-Z < hello.txt > HELLO.txt

echo "proprietary software sucks" | lolcat
yes "proprietary software sucks" | head | lolcat
yes "proprietary software sucks" | lolcat

take over the matrix (of text)

mosh / ssh
nvim
htop
tmux
sl

job control

^C
^Z
bg
fg
some_command &

other neat stuff

pbpst
curl