How to read text file line by line?

[wichbu]

What function can arduino UNO read each line in text file on a sd card?

[adafruit_support_bill]

The SD library read() function reads one byte at a time. To read a whole line, you need to allocate a buffer and write code to fill it one character at a time. Here is an example:
http://forum.arduino.cc/index.php/topic,202099.0.html