Handy Shell Commands for Beginners

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

Written on May 10, 2019 by Vivek Maskara.

Originally published on Medium