What are regular expressions used for?

        Regular expressions are used to define search patterns.

            In my pub directory is a file (/home/steve/pub/reg1.txt) that contains these lines:
                a3b
                    adcbcbc
                        12c5a36
                            a5
                                3c

                                        In the above file which line(s) will match the BRE "[a3][5c]" ?

                                                The last 2 lines

                                                        In the above file which line(s) will the BRE "^.3.*b" match?

                                                                The first line

                                                                    You have the BRE "wx*yz". Which of the following will match: wyyz wxxz wyz?

                                                                        wyz

                                                                            Write a BRE that will match any of these strings: 1a2, 1b4, 1c3, 1a3.

                                                                                "1[a-c][2-4]"

                                                                                    Write a BRE that will match empty lines (e.g. lines with nothing on them).

                                                                                        "^$"

                                                                                            Give the grep command to search a file called 'ztuff.dat' for lines that start with the word "zip" (regardless of case, so also match "ZIP" or "Zip") and is followed by 1 or more digits.  There is a file in my pub directory you can use to test your command.  Show me the exact command you used.

                                                                                                grep -i "^zip[0-9]*" ztuff.dat

                                                                                                    Give the grep command to remove all lines which start with the characters // and all blank lines from a file called 'code.cpp'.  There is a file in my pub directory you can use to test your command.  Give me the exact command you used.

                                                                                                        grep -vE "(//|^$)" code.cpp > code2.cpp