Add Print Out Files In Reverse as a unix til

unix/print-out-files-in-reverse.md

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+# Print Out Files In Reverse
+
+If you're familiar with `cat` -- the command you might use to print out a file
+in the terminal -- then you may appreciate a similar command: `tac`.
+
+With `tac` you can
+
+> Write each FILE to standard output, last line first.
+
+Notice that `tac` is `cat` spelled in reverse. That's what it does with your
+files, prints them out in reverse.
+
+Give it a try just as you'd use `cat`:
+
+```bash
+$ tac README.md
+```
+
+See `man tac` for more details.