The second piece to this puzzle is the "grep" command. This is one of the most obscure and easily-forgotten command names in Linux, but it is also one of the most useful. You can use "grep" to find patterns in data. For example, if you wanted to find every occurrence of the word "gold" in file "metals", you would type grep gold metals This would display every line of text in file "metals" that contained the pattern "gold". To use "grep" with a pipe, you simply leave out the file argument (just like we did with the "lpr -P zephyr" command on the previous page). For example, to list only those lines containing the word rabbit in Jester's joke files, you would type cat joke-1 joke-2 | grep rabbit See the example at right. Actually, an easier way to accomplish this would be to type grep rabbit joke* but that wouldn't have illustrated the use of "|". Click the right arrow.