Linux Shell – Script to check if a GNU/Linux package is installed

function instalado() {
#We check if the wget package is installed using the aptitude command

aux=$(aptitude show wget | grep "Estado: instalado")
if `echo "$aux" | grep "Estado: instalado" >/dev/null`
then
return 1
else
return 0
fi
}

# we call the function
instalado $1 &> /dev/null

#We check the result... if it gives 1 it is installed and if it gives 0 it is not installed. 

if [ "$?" = "1" ]
then

#If the package is installed I send a message

echo el paquete $aux ya esta instado.

#If it was not installed...for example we install it... 

else

apt-get install wget

fi

function instalado() {

#We check if the wget package is installed using the rpm command
aux=$(rpm -qa wget)

#We filter the result of the rpm command using grep and save the result.
if `echo "$aux" | grep "wget" >/dev/null`
then
return 1
else
return 0
fi
}

#We call the function 
instalado $1 &> /dev/null

#We check the result... if it gives 1 it is installed and if it gives 0 it is not installed. 
if [ "$?" = "1" ]
then

#If the package is installed I send a message

echo el paquete $aux ya esta instado.

#If it was not installed...for example we install it...

else

yum install wget
fi