+.TP
+.B \-M
+updates manual pages located in the set of directories specified by
+.I path
+(/usr/man by default).
+.I Path
+has the form of a colon (`:') separated list of directory names,
+for example `/usr/local/man:/usr/man'.
+If the environment variable `MANPATH' is set,
+its value is used for the default path.
+.PP
+If the nroff source file contains only a line of the form `.so manx/yyy.x',
+a link is made in the catx directory to the appropriate preformatted manual
+page.
+This feature allows easy distribution of the preformatted manual pages
+among a group of associated machines with
+.I rdist(1).
+The nroff sources need not be distributed to all machines,
+thus saving the associated disk space.
+As an example, consider a local network with 5 machines,
+called mach1 through mach5.
+Suppose mach3 has the manual page nroff sources.
+Every night, mach3 runs
+.I catman
+via
+.I cron(8)
+and later runs
+.I rdist
+with a distfile that looks like:
+.IP
+.nf
+.ta \w'${MANUAL'u
+
+MANSLAVES = ( mach1 mach2 mach4 mach5 )
+
+MANUALS = (/usr/man/cat[1-8no] /usr/man/whatis)
+
+${MANUALS} -> ${MANSLAVES}
+ install -R;
+ notify root;
+
+.fi