A shell script can use sqlite3 to access a database and provide a simple user interface. The next script implements the previous address database with sqlite instead of a flat text file. It provides three commands:

• init: This is to create the database
• insert: This is to add a new row
• query: This is to select rows that match a query

In use, it would look like this:

    $> dbaddr.sh init
    $> dbaddr.sh insert 'Joe User' '123-1234' 'user@example.com'
    $> dbaddr.sh query name Joe
    Joe User
    123-1234
    user@example.com

The following script implements this database application:

    #!/bin/bash
    # Create a command based on the first argument

    case $1 in
      init )
        cmd="CREATE TABLE address \
          (name string, phone string, email string);" ;;
      query )
        cmd="SELECT name, phone, email FROM address \
          WHERE $2 LIKE '$3';";;
      insert )
        cmd="INSERT INTO address (name, phone, email) \
          VALUES ( '$2', '$3', '$4' );";;
    esac

    # Send the command to sqlite3 and reformat the output

    echo $cmd | sqlite3 $HOME/addr.db | sed 's/|/\n/g'

This script uses the case statement to select the SQL command string. The other command-line arguments are replaced with this string and the string is sent to sqlite3 to be evaluated. The $1, $2, $3, and $4 are the first, second, third, and fourth arguments, respectively, to the script.