Here, placed side-by-side for comparison, are implementations of cat(1)
from GNU's coreutils, Plan 9, and others.  See addendum.txt for more
information.

All cat.c files (renamed by prefixing the name of the source of the
source) are presented, unaltered and in their entirety.  Note how easy
it is to read and understand plan9-cat.c (which should take only a
couple of minutes, possibly even for coders that don't know C). Other
than that, I think the files speak for themselves.

Keep in mind while reading that the cat utility's purpose is to
concatenate files.  (The obvious implied commentary aside, it is almost
like a collection of napkin doodles from artists: self-contained samples
of different styles.)

Lastly, here are the line and character counts, sorted:

  Lines   Chars Filename
-----------------------------
     35     531 plan9-cat.c
     43     589 xv6-cat.c
     46     724 p9p-libbio-cat.c
     48     955 busybox-cat.c
     48     986 inferno-cat.b
     52     824 sbase-cat.c
     63    1130 unix7-cat.c
     64     646 unix2-cat.s
     68    1530 toybox-cat.c
     69    1241 unix10-cat.c
    168    3299 ultrix-cat.c
    179    3301 readline-cat.c
    222    3948 4.3bsd-cat.c
    248    5581 openbsd-cat.c
    316    6952 netbsd-cat.c
    330    7297 dragonfly-cat.c
    394    7082 sunos-usrbin-cat.c
    428    8086 solaris-cat.c
    450    8619 sunos-5bin-cat.c
    474    8714 irix-cat.c
    511   11495 freebsd-cat.c
    543   13321 aix-cat.c
    782   22684 gnu-cat.c
   5581  119535 total