Handy Shell Commands for Beginners

Via Wikimedia Commons

Check if a file exists

if [ ! -f "/home/pi/test.sh" ]; then
echo "file exists"
fi

Check if a directory exists

if [ -d "/home/pi/test" ]; then
echo "test dir exists"
fi

Install Apt-Get Package

# update pip
# check if package is installed
# install package if not installed
installPackage() {
retval=0
echo "Installing package $1"
if [ $(dpkg-query -W -f='${Status}' $1 2>/dev/null | grep -c "ok installed") -eq 0 ];
then
echo "Package $1 is not installed"
if echo "yes" | sudo apt-get install $1; then
retval=1
fi
else
echo "Package $1 is already installed"
retval=1
fi
return "$retval"
}

Manually Set Date Time

sudo date -s '2019-05-10 09:07:00'

Setup SSH Keys

mkdir -p /home/pi/.ssh
sudo echo '' | ssh-keygen -t rsa -q -N '' -f /home/pi/.ssh/id_rsa

Turn Off Strict Host Checking For a Domain

echo -e "Host google.com\n\tStrictHostKeyChecking no\n" >> ~/.ssh/config