franciscoG98/bash

Bash

use vi or vim

quit vi/vim

:wq # or crash computer (whatever works for you)

shebang

!#

Run script

bash script.sh
bash greeetings.sh argument
bash web_status.sh (argument url with https://) # returns web status

Use variables and conditions

$()

if [ condition ]; then
	do smth
else
	do smth else
fi

Grant execution permission

chmod +x your_script.sh

so insead of

bash your_script.sh

you do

./your_script.sh

use multiple arguments

$@

Syntax

Function

function saludar () {
	echo Hola $1
}

For

function saludar () {
	echo Hola $1
}

for USUARIO in ${@}; do
	saludar $USUARIO
done

Case

function saludar () {
	echo Hola $1
}

case "${1}" in
	start)
		echo "Ejecutaste start"
		;;
	finish)
		echo "Ejecutaste finish"
		;;
	restart)
		echo "Ejecutaste restart"
		;;
	*)
		echo "Especificaste un argumento invalido"
esac

While

function saludar () {
	echo Hola $1
}

X=3

while [[ $X -ge 1 ]]; do
	echo "El valor de X es $X"
	X=$((X-1))
done

Flags

while getopts "a:b" FLAG
do
	case "${FLAG}" in
		a)
			echo "Pasaste la opcion '-a' al script"
			echo "El argumento de '-a' es ${OPTARG}"
			;;
		b)
			echo "Pasaste la opcion '-b' al script"
			;;
		*)
			echo "Uso invalido, por favor pasar opciones '-a' o '-b'"
			;;
	esac
done

the ":" after "a" flag allows to use the value of given argument with