bash myscript

chmod +x myscript && ./myscript

bash mysh.sh
sh myscript

#!/usr/bin/env bash

# comment

echo "$1 $2" # positional arguments passed one by one, e.g., bash myscript arg1 arg2
echo "$#" # number of arguments passed
echo "$@" # all arguments passed
echo "You are here: $PWD" # $PWD is the current path

MyVar="My string"
MyArray=(all in one)

echo $Variable
echo "This is my var: $Variable" # double quotes are required for interpolation
echo "${MyArray[@]:0:3}" # "all in one", because it prints 3 elements starting from the first (0)

# Be careful the following does not display a value
echo ${#MyArray[2]} # "3" as there are 3 chars in the third element of the array, which is the word "one"

MyVar="My variable"
# Length
echo ${#MyVar}

# Substitution
echo ${MyVar//a/O} # "My vOriOble"

# Expansion
echo ${!BASH@} # all variable names than begin with "BASH"
echo ${!BASH*} # all variable names than begin with "BASH"

# Removals
MyFile="list.txt"
echo ${MyFile%.*} # the filename without extension
echo ${MyFile##*.} # the file's extension

# Default value
echo ${AnotherOne:-"Another one"} # displays "Another one" even if AnotherOne is not defined

declare -A Movies

Movies[title]="The Dark Knight Rises"
Movies[bestActress]="Anne Hathaway"
Movies[director]="Christopher Nolan"

printf "%s\n" "Learn it" "Zip it" "Bash it" # it prints 3 lines
printf "%.*f\n" 2 3.1415926 # prints 3.14

for i in "${MyArray[@]}"; do
    echo "$i"
done

MyString="First Second Third"
for n in $MyString
do
   echo "$n line"
done

while [ true ]
do
    echo "We loop"
    break
done

echo {1..7} # 1 2 3 4 5 6 7
echo {a..g} # a b c d e f g

until [ $counter == 111 ]
do
    echo "Number is: $((counter++))"
done

echo "6x7?"
read answer
echo answer # hopefully 42 but can be anything the user wants

if [[ CONDITION1 || CONDITION2 ]]
then
    # code
elif [[ CONDITION3 && CONDITION4 ]]
then
    # code
else
    # code
fi

case $COLOR in

  Red)
    echo -n "red"
    ;;

  Blue | Green)
    echo -n "blue or green"
    ;;

  Yellow | "Sunny" | "Gold" | "Fire")
    echo -n "Yellow"
    ;;

  *)
    echo -n "What?"
    ;;
esac

#!/usr/bin/env bash
set -e

#!/usr/bin/env bash
if [ CONDITION ]; then
    exit 0 # 0 1 2 3 ... N
fi

# $? is the exit status of last command
if [[ $? -ne 0 ]] ; then
    echo "You failed!"
    exit 1
else
    echo "You are the best!"
fi

#!/usr/bin/env bash
set -x # set -n can also be used to check syntax errors
ARGS=("$@") # store all script args in a var

bash -x myscript

if [ ! -x "$PWD/myscript" ]; then
    echo "File is not executable!"
    exit 1
fi

echo {1..10}{0,5}h # bash 3
echo {10..120..10}km # requires bash 4

function test ()
{
    echo "$1 $2" # displays positional arguments passed to the function ("All" "In")
    return 0 # if you return a value, it !must be numerical!
}
test "All" "In"

printenv USER # if you don't specify a variable, all variables will be displayed

TEST="My test"

function test ()
{
    local MyVar="My string" # local variable
}
test

for r in $(ls $PWD)
do
    # task using the result of the command => r
    echo "$r"
done

function hello() {
    echo "Hello Ethan"
}

echo "This is the result of the function : $(hello)"

Users=$(cat users.txt)

read -p "Continue? [y/n]: " -n 1 -r
echo # extra line
if [[ $REPLY =~ ^[Yy]$ ]]
then
    echo "ok"
elif [[ $REPLY =~ ^[Nn]$ ]]
then
    echo "Too bad!"
else
    echo "Sorry, I did not understand your answer :("
fi

select w in "zsh" "bash" "powershell" 
do
  echo "You prefer $w"
  break  
done

alias lz='ls -alh'

wget -O /tmp/logo.jpg 'https://dev-to-uploads.s3.amazonaws.com/uploads/logos/resized_logo_UQww2soKuUsjaOGNB38o.png' && echo "echo only if the first hand is true"
wget -O /tmp/logo2.jpg 'https//example.com/logo.jpg' || echo "echo only if the first hand is wrong"
wget -O tmp/logo3.jpg 'https//example.com/logo.jpg' ; echo "echo whatever happens"

sudo !!

COMMAND > out.txt   # write in out.txt 
COMMAND >> out.txt  # append in out.txt 
COMMAND 2> test.log # stderr to test.log
COMMAND 2>&1        # stderr to stdout
COMMAND &>/dev/null # stdout and stderr to (null)

#!/usr/bin/env bash

trap 'catch' EXIT

catch() {
  echo "Exit game!"
}

echo "ok"
echo "---"

exit 0

#!/usr/bin/env bash

trap "rm /tmp/scan.txt" EXIT

#!/usr/bin/env bash

source ./otherScript

#!/usr/bin/env bash

set -eu # u is to exit if using undefined variables
set -o pipefail

bash

nohup bash script &

SUBDIRS=$(ls -d */)
for sub in $SUBDIRS
do
    echo $sub
done

mv /project/file.txt{,.bak} # rename file.txt.bak

ssh REMOTE_HOST 'bash -s' < myScript

find . -size +10M -print

touch {script1,script2,script3,script4,script5,script6,script7}

touch script{1..7}

#!/usr/bin/env bash

echo "Welcome aboard"
echo "What's the targeted IP?"
read TargetIp

if [[ ! $TargetIp ]]
    then echo "Missing targeted IP!"
    exit 1
fi

echo "What port do you want to scan?"
read PortNumber

if [[ ! $PortNumber ]]
    then echo "Missing port number!"
    exit 1
fi

nmap $TargetIp -p $PortNumber >> scan.txt # append results in scan.txt

alias whatsMyIp="echo $(ifconfig -a | grep broadcast | awk '{print $2}')"
whatsMyIp # IP local