To get newer man pages in OSX? I noticed that my manuals are very old in my system although all updates done. 
Etc man cmp tells about the flag -l

-l  --verbose
          Output byte numbers and values of all differing bytes.


while Wikipedia is about more fully


  Output the (decimal) byte numbers and (octal) values of all differing
  bytes, instead of the default standard output. Also, output the EOF
  message if one file is shorter than the other.


The last sentence was critical in my understanding of the output. 
I would like get more fully manuals to my system. 

Possible ways to get better manuals


cabal
homebrew
...?


How can you install better manuals to your terminal commands in OSX?
The best manual is the manual that is supplied with the command you are using whether that manual is old or new. Assuming that you have not hard coded MANPATH then man would determine the manual with your PATH and man.conf. If you are installing your own tools then possibly man.conf may need to be configured with your installation prefix. 

If you have duplicate tools installed then the manual for the command first in your PATH is presented. You can read another manual by pointing man to the directory in which that man page resides.

    man -M /path/to/share/man COMMAND


You can read all the manuals of a particular command.

    man -a COMMAND