How can we give the check on shell script?

Question

Any one can help me do this with shell script:

1. When VM startups, it checks if a folder (dbsync-installdir) exists
2. if it does not exists, it will download the ZIP file using wget.

Answer 1

To check check if a directory doesn't exist:

if [ ! -d "$DIRECTORY" ]; then
    # Here if $DIRECTORY doesn't exist.
    wget http://url_to_zip_file
fi

To extract zip files see man unzip

Also you can check if a directory exists:

if [ -d "$DIRECTORY" ]; then
    # Here if $DIRECTORY exists.
fi