Output grep results to text file, need cleaner output

Question

When using the Grep command to find a search string in a set of files, how do I dump the results to a text file?

Also is there a switch for the Grep command that provide

Answer 1

grep -n "YOUR SEARCH STRING" * > output-file

The -n will print the line number and the > will redirect grep-results to the output-file.
If you want to "clean" the results you can filter them using pipe | for example:
grep -n "test" * | grep -v "mytest" > output-file will match all the lines that have the string "test" except the lines that match the string "mytest" (that's the switch -v) - and will redirect the result to an output file.
A few good grep-tips can be found on this post