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Bash Commands

 
  • Jan 23, 2021

list all running services

systemctl list-unit-files

listing, adding and removing tools

apt-cache search pure-ftpd
apt show pure-ftpd | less

reading user input

#! /bin/bash  
echo “Hello there, would you like to learn how to hack: Y/N ?”  
read answer  
echo “Your answer was $answer

reading user input 02

#! /bin/bash
# prompt the user for credencials

read -p ‘Username:  ’ username
read -sp ‘Password: ’ password

echo “Thanks, your creds are as follows: ”  $username ” and “ $password

if, else, elif statements

→ if.sh

#! /bin/bash
# if statement example

read -p “What is you age: ” age

if [ age -lt 16 ]
then
    echo “You might need parental permission to take this course!”
fi

→ else.sh ```bash #! /bin/bash

else statement example

read -p “What is you age: ” age

if [ $age -lt 16 ] then echo “You might need parental permission to take this course!” else echo “Welcome to the course” fi


> → elif.sh
```bash
#! /bin/bash
# else statement example

read -p “What is you age: ” age

if [ $age -lt 16 ]
then
    echo “You might need parental permission to take this course!”
elif
    [ $age -gt 60 ]
then
    echo “Hats off to you, respect!”
else
    echo “Welcome to the course”
fi

for loops

→ one liner

for ip in $(seq 1 25); do echo 10.11.1.$ip; done

→ one liner sequence expression

for i in {1..254}; do echo 10.11.1.$i; done

while loops

#! /bin/bash
# while loop example

counter = 1
while [ $counter -le 10 ]
do
    echo “10.11.1.$counter”
    ((counter++))
done

functions

#! /bin/bash
# function example

print_me () {
    echo “You have been printed!”
}

print_me

→ with argument ```bash #! /bin/bash

passing argument to the function

pass_arg () { echo “Today’s random number is: $1” }

pass_arg $RANDOM


> → return value example  
```bash
#! /bin/bash
# function return value example

return_me () {
    echo “Oh hello there, I'm returning a random value!”
    return $RANDOM
}

return_me
echo “The previous function returned a value of $?”
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