Learn Linux

based on boot.dev

resources (redhat blog, ibm docs, digitalocean community)

Terminales y Shells

echo "Hello world"

Historically a terminal was "physical terminal", a device to type commands (a keyboard and a screen). Today means "terminal emulator". This one lets you type commands into a window on your computer (responsible of drawing text on screen, process keystrockes).

Shell mainly do the magic (Read, Eval, Print, Loop). optimized for running other programs, writing small scripts.

ex: expr 123456 + 7890

name="Lane"
$ echo Hello $name
Hello Lane

history    clear

Sistemas de archivos

.  : working dir (pwd)
.. : parent dir (pwd)
/  : fs root
~  : home (/home/user)

cd    ls

cat file1.txt file2.txt

head -n 10 file1.txt    tail -n 10 file1.txt

less -N 2023.csv # show numbers

command1 ; command2    command1 && command2 # if first success, second run

touch file.txt

mkdir my_directory   mv   rm -rf   cp -R

grep "hello" words.txt    grep -r "hello" . --exclude-dir="backups" # recursive

find some_directory -name hello.txt    find some_directory -name "*chad*" # wildcards

ex: curl -L https://github.com/bootdotdev/worldbanc/archive/refs/heads/main.zip -o worldbanc.zip
    unzip worldbanc.zip
    rm worldbanc.zip
    mv worldbanc-main worldbanc
    sudo chown -R $(whoami) worldbanc
    sudo chmod -R 755 worldbanc

Permisos

drwxrwxrwx
- : file
d : dir

(owner, group, others)    (read, write, exec)
                           rwx: All permissions
                           rw-: Read and write, but not execute
                           r-x: Read and execute, but not write

ex: -rwxrwxrwx: A file where everyone can do everything
    -rwxr-xr-x: Everyone can read and execute, but only owner can write
    drwx------: Only owner can read, write and execute

chmod -R u=rwx,g=,o= DIRECTORY    chmod u+x program.sh # or -x

sudo chown -R root DIRECTORY

Programas

mydir/program.sh # unless ./

compiled, interpreted programs

which sh    cat /bin/sh

#! interpreter [optional-arg]
#!/usr/bin/python3

env # environment variables

WARN_MESSAGE="this works too" ./warn.sh # local

export NAME="Lane"

echo $PATH    /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
export PATH="$PATH:/path/to/new"    source ~/.bashrc

Entrada/Salida

man man    --help    -h    help

ex: wc -c

exit-status 0: success 1: general error # another is error

echo $?    # 0    # non-zero (depends on your OS)

unset ENV_VAR_NAME    export ENV_VAR_NAME=""

data-streams (stdout, stderr)    > # redirect to file    2>

stdin    read VAR

echo "Have you heard the tragedy of Darth Plagueis the Wise?" | wc -w

ctrl+c: SIGINT # interrupt

ps aux | grep malicious.sh
kill PID
top (M sort by ram)

Unix Philosophy (write programs that)
  do one thing and do it well
  work together
  handle text streams (universal interface)

Paquetes

webi is an anti-package manager (install cli tools from web).