"xtail" watches the growth of files.  It's like running a "tail -f"
on a bunch of files at once.

You can specify both filenames and directories on the command line.
If you specify a directory, it watches all the files in that
directory.  It will notice when new files are created (and start
watching them) or when old files are deleted (and stop watching
them).

This program is an oldie but goodie.  It was posted to comp.sources.misc
in July 1989 (see ftp.uu.net:/usenet/comp.sources.misc/volume7/xtail.Z).
I remember posting an even earlier version to alt.sources.  It has
been published in the O'Reilly & Associates "Unix Power Tools"
collection (book and CD-ROM).  Over the years, some fly-by-night
organizations (such as the MIT X Consortium and SGI) have tried to
steal the "xtail" name.  Don't be fooled!  Insist on the original.