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I was searching Unix vs OS X. I found a notable difference at From http://www.unix.com/unix-dummies-questions-answers/919-mac-osx-vs-unix.html

OS X is a evolutionary kernel from the MACH and BSD linage.

Can anyone help me understand this?

What are the notable differences between Unix and Mac OS X.

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Related –  Emanuel Berg Apr 21 '13 at 20:01
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3 Answers

Regarding an explanation of the explanation:

See the FreeBSD forum. Basically the OS X userspace is essentially FreeBSD (with small elements of NetBSD) but the kernel itself is a fork of the MACH Kernel that makes it more monolithic in nature (like the network stack and process model are in line with FreeBSD). For a technical description, you'll probably have more luck googling "Darwin" than "OS X" since the latter has a lot of noise in it from people uninvolved with the project.

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+1 for good points. –  Mahbubur R Aaman Apr 21 '13 at 15:25
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Need differentiate the points of views:

From the shell-users point of view here is no big differences. OS X is fully certified Unix operating system, so it's command line is fully compliant with Unix standards and POSIX. You have terminal with shell, all shell commands (BSD style), you can install e.g. macports for GNU-versions of commands. e.g. the bundled sed is without --long argumnets, when you install macports you will get gsed - the GNU version. You have common directory structure as /bin /sbin /usr/bin .etc..

From the X-windows-user point of view - you can use X-windows apps, but it is not the default GUI. OS X has own GUI (called Cocoa). For an good overview you shoudl read this developer doc.

From the point of view system-admin - here is some bigger differences. Many configurations are done with Apple's own tools (mostly GUI) - but all tool has comman line interface too - but is IS a bit different from common UNIXes.

The biggest differences are for developers. OS X using fully object oriented message passing Objective-C. The Mach kernel IS message passing oriented kernel. Developing with xcode (Apple's development tool) is really easy.

I'm after using many different unix flavors over the last 20+ years (starting with BSD 2.9 on PDP11, via BSD 4.2/VAX, XENIX, SCO Unix, Consensys, Linux and FreeBSD) now using OS X nearly ten years. IMHO it is the best UNIX what I used anytime - so therefore the answer is subjective...

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+1 for "Many configurations are done with Apple's own tools (mostly GUI) - but all tool has comman line interface too - but is IS a bit different from common UNIXes." –  Mahbubur R Aaman Apr 22 '13 at 5:52
note: the equivalent of X11 in OS X is Quartz. Cocoa is more like Qt or GTK+. –  strugee Feb 9 at 21:03
@strugee - ofc, youre right! ;) Here is an nice topic about the layers: developer.apple.com/library/mac/referencelibrary/GettingStarted/… –  jm666 Feb 10 at 0:00
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The UNIX trademark is owned by the Open Group, who use UNIX as a certification mark for SUS conformance. In that sense, OS X (or some versions of it) are UNIX, but Linux distributions and other BSD distributions are not. See http://www.opengroup.org/downloads/UNIX-certprog.pdf and http://www.opengroup.org/openbrand/register/. Parts of the Linux kernel intentionally don't comply to POSIX. The SUS certification is also expensive, and Linux distributions follow the Linux standard base instead.

BSD was originally based on Version 7 UNIX, but GNU and Linux were written from scratch. GNU/Linux is not usually considered to be genetic UNIX, but Darwin could be.

OPENSTEP was based on 4.3 BSD, but Darwin has used FreeBSD as a "reference platform". Many of the same developers work on Darwin and FreeBSD. Many OS X man pages are almost identical to (old versions of) FreeBSD man pages. But for example cp and ls have OS X-specific options for supporting extended attributes. There aren't any single current BSD versions of shell commands like there are with GNU, so I think it's more accurate to say something like OS X's sed or BSD seds than BSD sed.

Darwin is mostly licensed with the Apple Public Source License. APSL allows linking with proprietrary files, so it is not compatible with GPL. But unlike the BSD licenses, it requires derivative works to release source code.

Related questions:

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FWIW BSD doesn't prevent forks from releasing source code, they just don't prevent you from closing the source code. It's not the anti-GPL it's just un-GPL. –  Joel Davis Apr 21 '13 at 23:54
+1 for good answer. –  Mahbubur R Aaman Apr 22 '13 at 5:51
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