Introduction to the CLI
cd ~/,cd /home/brutusandcd $HOMEandcdare equivalent- root can refer to the “top of a directory tree (e.g. /)” OR a user with elevated privileges (e.g. admin)
- never run a web browser as root . . . . natural selection at its finest
- NEEDS EXAMPLES
- NEEDS EXAMPLES
- NEEDS CLARIFICATION
- awk
- python
- && (and)
- || (or)
- & (background)
- | (pipe)
- visudo
- git
- apt-get
- pacman
- yum
- systemctl
- wifi-menu
- mogrify
- chmod
- chown
- date
- less
- htop
- figlet
- wget
- curl
- last
- dmesg
- sponge
- xargs
This week’s meeting will be an introduction to the command line. We recommend having a Linux distribution installed or having one in a VM so you can follow along.
As always, laptops are encouraged and pizza will be provided.
At the end of the meeting, many of you requested that I put up the list of commands that I was working off of throughout the meeting. Below is a copy of the notes that I was working off of. We didn’t get through all of them, and I expanded on some of them quite a bit, and some of them have notes (like NEEDS EXAMPLES, etc.) but hopefully they’re helpful to someone.
Introduction to the Command Line
Commonly Asked Questions
Q) Why won’t my terminal let me type anything into the password prompt?
A) blindly type in your password and hit enter . . . . just do it
Fundamentals
list files in the current directory
ls
change directories
# go to a user's home directory
cd ~
# move up one directory
cd ..
# go to the root directory
cd /
list files in the current directory, including hidden files
ls -a
list files with details (permissions, owner, size) in the current directory
ls -l
combine both of the above, i.e. detailed list of files, including hidden files
ls -al
any of the following are equivalent
ls -al
ls -la
ls -l -a
ls -a -l
create a new duplicate of ‘foo’ named “bar” in the current directory
cp foo bar
relocate/rename a file or folder
# relocate folder "homework" to a different parent directory
mv ~/documents/homework ~/college/homework
# relocate folder "homework" to a different parent directory AND rename it to "bs"
mv ~/documents/homework ~/college/bs
create a new folder named “foo” in the current directory
mkdir foo
create a new empty file named baz
touch baz
output the contents of file “helloworld.txt”
cat helloworld.txt
show the path to the current directory
pwd
view a visual hierarchy of files & folders inside of the current directory
tree
delete a file named “foo” in the current directory
rm foo
delete an empty directory named “bar”
rmdir bar
delete a directory named “baz” and all its contents
rm -r baz
outputs file baz.txt with line numbers
nl baz.txt
reset terminal screen, i.e. clear its output and put your prompt back at the top
clear
can also be done with ctrl-l (hold control key and press “l”)
reset the terminal screen and reinitialize terminal settings - use this when your terminal is showing weird symbols or otherwise in an unknown state
reset
view the syntax manual for any given command
# view the documentation for the command "less"
man less
# view the documentation for the command "tail"
man tail
# you can even view the documentation of "man" with "man" . . . oh man that's confusing
man man
Execute command foo as super-user(full permissions)
sudo foo
What do you mean ‘permission denied’? Do that last command with super user
# this is INCREDIBLY DANGEROUS if abused
sudo !!
Execute graphical program gparted as super-user on gnome
gksu gparted
Execute graphical program gparted as super-user on kde
kdesudo gparted
Execute graphical program gparted as super-user on any desktop environment
pkexec gparted
–>
Intermediate
conditionally execute commands
create a folder named "documents" AND navigate to it
mkdir documents && cd documents
run a command in the background
htop &
list the process id of firefox
pidof firefox
restart your machine
shutdown -r now
restart your machine
shutdown -h now
list all files owned by brutus
find .-user brutus
change the current user’s password
passwd
elevate to super user
su
switch to user tux
su - tux
flavors of kill
# stop process with id "xxxx"
kill xxxx
# stop multiple processes with ids "xxxx", "yyyy", "zzzz"
kill xxxx yyyy zzzz
# stop process with that includes the string "fox" in its name
pkill fox
# stop process with the explicit name "firefox"
killall firefox
# nuke process with the explicit name "firefox"
killall -9 firefox
Practical Commands You Should Learn
test your internet connection
#it works with ip addresses
ping -c 3 8.8.8.8
# or even urls
ping -c 3 google.com
tip: this is a great way to troubleshoot DNS issues
list all disk partitions
df -h
output kernel version
uname -r
overwrite baz.txt and with “foobar”
echo "foobar" > baz.txt
append “foobar” onto the end of baz.txt on a new line. -e makes echo respect newlines.
echo -e "foobar-1\nfoobar" >> baz.txt
print the contents of baz.txt
cat baz.txt
write and create bar.txt
cat > bar.txt
Find lines that match a pattern in a file
echo -e "line1\nline2\nline3" > grep_test.txt;
grep '2' 'grep_test.txt'
# Only show one file as soon as a match is found
grep -l 'line' grep_test.txt
# Match multiple patterns
grep -e '2\|3' grep_test.txt
Substitute patterns in a line or file
echo "one two three" | sed 's/two/three' sed_test.txt
Copy one block device to another block device. Known as ‘Destroyer of Disks’
dd if=~/Downloads/latest-ubuntu.iso of=/dev/sdb status=progress
zip the files bar.txt and baz.txt
zip -r foobar.zip bar.txt baz.txt
extract foobar.zip
unzip foobar.zip
Create tape archive that’s gzipped
tar cvzf /tmp/dest_file.tar.gz /tmp/src_files/
Extract tape archive that’s gzipped
tar xvzf /tmp/dest_file.tar.gz
spawn a static web server in the current directory on port 8080
python -m SimpleHTTPServer 8080
output ip address
ip addr show
outputs the machine’s hostname, duh
hostname
The Most Important Commands
make a cow say moo
cowsay moo
list all cows available for use
ls /usr/share/cowsay/cows
use an alternate cow (in this case the unipony)
cowsay -f unipony "everypony loves me!"
make people think you’re hacking
cmatrix
make people think you’re hacking incorrectly
cat /dev/urandom | cmatrix
make really large text
toilet hello world
get helpful advice
fortune
git commit with style
git commit -m $(fortune)
watch Star Wars
telnet towel.blinkenlights.nl
Compose music from entropy in /dev/urandom
cat /dev/urandom | hexdump -v -e '/1 "%u\n"' | awk '{ split("0,2,4,5,7,9,11,12",a,","); for (i = 0; i < 1; i+= 0.0001) printf("%08X\n", 100*sin(1382*exp((a[$1 % 8]/12)*log(2))*i)) }' | xxd -r -p | aplay -c 2 -f S32_LE -r 16000