How to select rows from a log file?

https://drive.google.com/file/d/0B4opCeiIoNAMTE9rTW9adVNNV0E/view?usp=sharing The link contains codes and 3 files(1 is a txt file and 2 & 3 are log files). File 1 is processed by button 1 whiles file 2 and 3 are processed by button 23. When button 23 is pressed it gives the opportunity for button 2 and 3 to be displaced for the respective files to be opened and read. However, I am having errors.

What I wanted to do was that for each case read the corresponding file and save them in columns (columns 1 to 15). Making sure that only rows with $GNGGA are read and saved in the case 3.

What codes do I need to select rows with $GNGGA?

[Walter Roberson]

Duplicates http://uk.mathworks.com/matlabcentral/answers/230539-how-to-read-files-of-different-types

[AbelM Kusemererwa]

Robertson, I tried the codes for the 3.log in the attached file but did not work