simple matlab script to remove certain strings from txt file

There will be a text file that looks something like this: $KEEP,16 $REMOVE,20 $KEEP,17 $REMOVE,201 $KEEP,12 $REMOVE,2012 I want to create a matlab file that will allow me to read from the above text file and generate another text file that looks something like this: $KEEP,16 $KEEP,17 $KEEP,12 Basically, preserver only the lines with the word "KEEP" in it and remove the rest (eg. $REMOVE... and break line) the generated file should have the same file name as the orginal, but placed in a sub directory.