CLI-bash 101

Command Line (CLI)

• CLI: Command Line Interface
• Terminal: the application window you type into
• Shell: the program inside the terminal that interprets your commands
• Bash: Bourne-again shell → UNIX shell
• Console

And basically, it is a text-based way to interact with your computer.
→ user interacts with Operating System (OS), the computer, through a Graphical-User Interface (GUI) — that is this CLI

Essential cmds

• some cmds
  • opt+arrow : move cursor one word
  • ctrl+a and ctrl+e : go to beginning, end of the line
• some options :
  • . (or ./): current directory
  • .. : parent directory
  • ~ : user home directory
  • * : all files in current directory
  • -R : content of a folder, recursively
  • -h or --help or info or man : help
  • -v or --version : version
  • -u : user action instead of a root action
  • > : send output to a file, overwrite
  • >> : send output to a file, append
  • *.extension
• open : open a file, or a finder window to the dir
• ls : lists files in current directory
• pwd : path to working dir(ectory)
• cd : change directory, or go home if no param
  • cd - : previous directory visited
• mkdir : make directory (i.e. create folder)
  • mkdir -p folder1/folder2 : nested folders
• touch : create new file
• man for manual / documentation
• cp & mv [ori_path] [target_path] : copy & move file from a path to another path (or rename)
  • cp -R : for folders, add the option ‘-R’ for recursively
  • cp file.txt . : copy file.txt to current directory
• rm : remove file or directory
  • rm -r : remove directory
  • rm -i, rm -f : remove interactive, forcefully
• find [dir_path] -name ["file"] : search for files in dir_path whose name is file
• grep ['text'] [file] : search ‘text’ in file
  • -i : case-INsensitive
  • -n : line
  • -c : count the number of appearances
  • -r : recursively does the search in the entire dir
  • -w : entire word only
  • -v : inverse search
  • --color : color display
• cat : output/print the content of a file
  • head / tail : output the first/last 10 lines of a file
• echo or printf : write text
  • echo 'hey' >> [file] : append ‘hey’ to file (same with printf)
  • echo 'hey' > [file] : overwrite ‘hey’ to file
• Chaining & piping :
  • [cmd_a];[cmd_b] : run A, then B
  • [cmd_a]&&[cmd_b] : run A, then B if A passed
  • [cmd_a]||[cmd_b] : run A, then B if A failed
  • [cmd_a]& : run A in background
  • [cmd_a]|[cmd_b] : run A, then pass the output of A to B
• clear: clear terminal display
• reset: proper reset + clean

• list the available serial ports

ls /dev/tty.*
ls /dev/cu.*

• sudo [cmd] : run cmd as a superuser (SUper user DO)
• top : display live info about current running processes
• du -h : memory used by files
• brew: package manager to install other tools on macOS
  • brew install [sth] : install a package
  • brew uninstall [sth] : uninstall a package
  • brew doctor : check brew for potential problems
• Exit/Quit/Less in commands:
  • :q!
  • q
  • :qa
  • ctrl+d or ctrl+z : stop operation
  • ctrl+c : terminate operation
  • ctrl+\\\\ : SIGQUIT sig, i.e. exterminate operation
• load bash profile in terminal
  • source ~/.bash_profile

bin : subdirectory containing executable programs

sudo apt-get install xxx
sudo apt-get update
sudo apt-get upgrade

network specifics

• ipconfig getifaddr en0
  • get local ip address
• ipconfig getoption en0 domain_name_server
• ipconfig getsummary en0
  • get summary
• ifconfig | grep broadcast
  • my wifi info
• curl ifconfig.me
  • get public ip address
• hostname
  • get machine hostname
• arp -a
  • list all devices connected to local network
• ping -c 1 192.168.86.241

http://localhost:8080/

can be accessed by devices on the same network, with the use of local IP addresses,

http://[YOUR-IP-ADDRESS]:8080/
http://192.168.1.15:8080/

note: sometimes, it’s also worth modifying / removing the “http(s)://” part.

python specifics

• python -V: which version
• which python: what installation is used for what command
  • which python3
  • which -a python python3: show full paths of all exe named python or python3

misc

sudo pkill coreaudiod — gently kill all audio deamon process

• GET https://example.com/api/end-point-name?key=your-api-key
  • to request

Bash script 101

• create a bash script:
  • #!/bin/bash = a “shebang” which tells the system to use Bash shell to exe this script
  • chmod u+x : change moderator rights/permissions & convert file into an executable file
    • chmod 700 is equivalent
  • ./ in this current directory, + name of the exe → run the script

touch bashcmd
echo '#!/bin/bash' > bashcmd
echo 'echo HelloWorld!' >> bashcmd
chmod u+x bashcmd
./bashcmd

another example of bash file

#!/bin/bash

var = 'world'
echo Hello var!
echo "Hello $var"

current_date=$(date)
echo "Today is $current_date"

• declare a variable : var = "hey"
• read a variable : echo $var
• read var : user input for the value of var

echo "What is your favorite color?"
read color # The user's input is stored in the variable 'color'
echo "You said your favorite color is $color. Nice!"

• conditional statements

echo "Enter a number:"
read number
 
# Note the spaces! They are important.
if [ $number -gt 10 ]; then
    echo "That's a large number."
elif [ $number -eq 10 ]; then
    echo "That's exactly ten."
else
    echo "That's a small number."
fi

• -eq: Equal to
• -ne: Not equal to
• -gt: Greater than
• -lt: Less than
• -ge: Greater than or equal to

and for strings:

• =: Equal to
• !=: Not equal to

can also loop through a list:

for fruit in apple banana orange; do
    echo "I like $fruit"
done
 
# This will list all .txt files in the current directory
for file in *.txt; do
    echo "Found text file: $file"
done