Simple Database Solution (local Storage) From Bash

I am searching for an simple data storage solution, interfaced from local bash (write and read).

Background: I'm collecting sensor data and save values with timestamp (actually in a text file, every week a new file is created). I like to visualize the data on request with the help of php. Is there a database (like sqlite) which can be easily written from bash ?

You could try rrdtool. It's a round robin time series db, perfect for visualizations.