#GNU

LOC	File
5629	ls.c
2	ls-ls.c
2	ls-dir.c
2	ls-vdir.c
10	ls.h
5645	Total

#POSIX

Not mentioned in the man page

#Notes

• all the C files were in the same subdirectory; there was no organization by binary
• dir and vdir were implemented as well

#FreeBSD

LOC	File
1024	ls.c
839	print.c
236	util.c
213	cmp.c
89	ls.h
80	extern.h
2481	Total

#POSIX

From the man page:

With the exception of options -g, -n and -o, the ls utility conforms to IEEE Std 1003.1-2001 (“POSIX.1”) and IEEE Std 1003.1-2008 (“POSIX.1”). The options -B, -D, -G, -I, -T, -U, -W, -Z, -b, -h, -w, -y and -, are non-standard extensions.

#OpenBSD

LOC	File
13	main.c
619	ls.c
382	print.c
70	util.c
167	cmp.c
57	utf8.c
77	ls.h
54	extern.h
1439	Total

#POSIX

From the man page:

The ls utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification, except behaviour for the -o flag differs.

The flags [-hT], as well as the BLOCKSIZE environment variable, are extensions to that specification.

The flags [-go] are marked by IEEE Std 1003.1-2008 (“POSIX.1”) as being an X/Open System Interfaces option.

Historically, the -g flag was used to specify that the group field be included in long listings. The group field is now automatically included in the long listing for files and the meaning of the -g flag has been changed in order to be compatible with the IEEE Std 1003.1-2008 (“POSIX.1”) specification.

#NetBSD

LOC	File
50	main.c
717	ls.c
579	print.c
168	util.c
199	cmp.c
81	ls.h
53	extern.h
1847	Total

#POSIX

From the man page:

The ls utility is expected to be a superset of the IEEE Std 1003.2 (“POSIX.2”) specification.