purest UNIX operating system?
 

I've been trying to understand some things to do with the UNIX, Linux relationship. My guess is that UNIX or C is the terminal system language of Linux, but how does this vary from distro to distro?

I've noticed that the syntax in some books varies slightly, some using # or ~ for root/superuser access access and $ for ordinary. Is there a good on line source for this?

Also, what is the purest UNIX o/s; FreeBSD, Solaris and in terms of learning terminal commands, would there be any difference between these and Ubuntu?

You should read:

http://en.wikipedia.org/wiki/C_(programming_language)
http://en.wikipedia.org/wiki/Unix
http://en.wikipedia.org/wiki/Unix-like
http://en.wikipedia.org/wiki/BSD
http://en.wikipedia.org/wiki/Linux
http://en.wikipedia.org/wiki/Solaris_(operating_system)
http://en.wikipedia.org/wiki/Ubuntu
http://en.wikipedia.org/wiki/Shell_(computing)
http://en.wikipedia.org/wiki/Bourne-Again_shell
http://www.gnu.org/software/bash/manual/

AFAIK, ~ refers to the home directory of a currently logged in user (regardless of the fact whether it's root or an ordinary user):
Logged in as root ~ refers to /root directory. Similarly, if you are logged in as eg. john, ~ will point to /home/john.

OK, let's take a shot at this: when you say UNIX, you're really talking about AT&T UNIX System V Release 4 (SVR4). Written almost entirely in C (there used to be a couple of assembly language pieces but those have pretty much gone the way of the dinosaurs), same with Linux -- the kernel is, pretty much, written in C (there may be some C++ stuff in there, I dunno, haven't looked lately, but essentially, the kernel in both SVR4 and Linux is C). Sun Microsystems Solaris operating system is SVR4 (as is, I believe, Apple's OS X and a few other offerings out there). For all practical purposes, it's difficult to tell the differences unless you dig deeply into the guts of the things.

Where you really see differences, though, is the utilities; the stuff you use all the time. GNU utilities (which almost all of them are in a Linux distribution) are not the same as AT&T versions -- GNU is an acronym for Gnu's Not Unix (and there's a whole philosophy surrounding that). The AT&T versions tend to be built around M. Douglas McIlroy's Unix Philosophy (roughly, a program or function should do one thing and do it well) where the GNU versions tend to add functionality (which some folks call "bloat"); human beings seem to be unable to leave well enough alone, methinks.

The pound sign, dollar sign thing (the terminal prompt) just goes back to the good old days when you worked on a Teletype and the command prompt let you know that you were working as the super-user (the pound sign) or as a non-privileged user (the dollar sign). The tilde is a shorthand for your home directory. UNIX was developed at Bell Laboratories on Teletypes; the reason many utility names are only two or so characters? It takes about ten pounds of pressure to type on a Teletype (and they're pretty much blaze along at about 30 characters per second on a good day). If you don't like the pound sign, dollar sign, you can assigned anything else you want to the environment variables PS1 and PS2; e.g., here's a section from /etc/profile that does that
I use Korn Shell, so my command line prompts are the "ksh" ones, PS1='${HOST}-${USER}-${PWD}: ', your mileage may vary.

So, what's "pure?" Well, nuthin, to be truthful; everybody adds something. BSD split off from AT&T's version (at about UNIX System 3, for lack of a better term), the Free Software Foundation (that's GNU) began building look-work alike utilities about then (we're talking early-to-mid 1980's here), a kid in Finland like what he saw in UNIX and sat down to write a look-work alike (and we all know how that turned out), SCO bought UNIX from AT&T (and that doesn't seem to be working too well), and the lowest common denominator (anything made by Microsoft) dominates, sigh. About as close as you're going to get is Solaris; in the Linux world, Slackware is the most un-fooled-around-with Linux distribution (I bounce back and forth between Solaris and Slackware and it's hard to tell the difference most of the time). Ubuntu? Well, Ubuntu does a lot of things for you and some folks find that annoying; for here can be interpreted as to; my personal opinion (for whatever that's worth) is that Ubuntu is excellent for folks migrating from Microsoft to a real operating system, nothing wrong with it, kinda nice, but...

It all gets down to you and what you want; Linux gives you the opportunity to try a distribution and if you don't like it for whatever reason, go try another distribution. Once you're comfortable with the utility set and can get around and do things, you'll start to notice the subtle differences from one to the next and you'll settle on something you're comfortable with.

If you're interested in pursuing this, you can look at and download source code for various versions of UNIX from links at The UNIX Heritage Society (http://www.tuhs.org) and The Heirloom Project (http://heirloom.sourceforge.net/index.html), where you can download almost all the standard SVR4 utilities and build them on your Linux system; kinda cool, that one.

Hope this helps some.

That good day must have been long after Unix was invented. When Unix was invented Teletypes were strictly 10 CPS.

30 CPS devices that were otherwise almost compatible with Teletypes were invented years later.

Teletypes had 7 bit characters in 11 bit frames at 110 bits per second. Those later devices had 7 or 8 (depending on model) bit characters in 10 bit frames at 300 bits per second.

I'm not sure what you mean by ten pounds of pressure. The pressure at which you needed to press the keys of a Teletype was more than required on an electric typewriter, but far less than needed on a mechanical typewriter and certainly not ten pounds. Any 30 CPS model I ever saw had exactly the keyboard characteristics (pressure, tactile feedback, etc.) of a standard electric typewriter, which means too little key pressure rather than too much. As keyboard ergonomics improved, the keyswitch pressure on a good quality keyboard has become slightly higher than on an electric typewriter from the 60's or 70's, not lower.

AT&T Unix was sold to Novell (and who still own the rights ... which SCO found out the hard way).
Prior to that AT&T and SUN did some worked together.
BSD was spun off from AT&T Unix very early on.

The "terminal system" is governed by the shell (command interpreter) that is running.

Korn (ksh), Bourne (sh), Bourne again (bash), C shell (csh) ... etc.

Oh, duh! A slip of the synapses, I suppose -- yeah, 110 baud, 10 CPS, slower than the average typist, oiled paper tapes (kind of nice for "long-term storage" and "program loading"). The ASR 33's that I used caused a whole lot of fatigue after a few hours of whacking away at the keyboard and... ten pounds? Well, sure seemed like it at the time (especially compared to an IBM electric typewriter or a Royal manual). Moving on up to an Anderson-Jacobsen with those daisy-wheel heads, forms tractor and, holy toot, 1200 baud... ah, heaven.

Still miss those things.

purest UNIX operating system?
 

Wow, what responses. To think that this time last year, I thought Microsoft was the best operating system in the world. Now, I'll choke if anyone mentions them...

Having migrated from XP to Ubuntu, which is a really good system for beginners (probably the best for this), as well as having tried Puppy which is great for low RAM pc's, it is now time to look for something different.

I'm definitely going to take into account these postings and try out some new o/s' and no doubt will be back again on the forum. It's ashame Microsoft wasn't beaten in the personal pc market by Linux/UNIX. We would have all been spared wasted life moments and general irritation...

Why do you ask about unix anyway? I don't remember the whole history of unix/linux, but as far as I know, you'll be better off having any linux distro on your desktop. Correct me if I'm wrong, but if someone is interested in unix now (we're talking about private desktops), it must be only for historical purposes. As I said, I might be far from the truth, but that's my impression (having used linux for the last 4 years)

purest UNIX operating system
 

I was just really interested in the Linux/Unix connection and have noticed that Solaris and BSD don't seem to categorise themselves as Linux, rather more as UNIX.

Well, here's a graph/map of Linux derivatives: http://www.kde-files.org/CONTENT/con...218-gldt76.png
There's a load of history, inc derivative graphs for Unix here: http://www.levenez.com/unix/

What you call the terminal system language is determined by the shell you use. On most linux distros that's bash, but there are others like ksh, csh (and many derivatives), zsh and some others. These has nothing to do with C (other than the fact that some -all?- of them are programmed in C themselves). The only one whose syntax resembles in some way to C is csh. But it isn't -by any means- compatible at syntactical level with C. It wouldn't make much sense for a command interpreter anyway.

As for the symbols used for the prompt, that's merely a graphical thing that can be changed at your desire. It's the convention to use # for root adn $ for regular user (~ is used to mean $HOME, the home dir). But it can really be set to any other thing you like.

There are a number of OSes which are derived conceptually from the original AT&T unix, however, Linux Is No UniX. It's just a free kernel that someone built to act in a similar way to this of UNIX, including POSIX complicance and a similar paradigm that built strongly based around the concept of files and the file system.

There are a number of commercial UNIXes, and lots of different OSes that resemble UNIX to a bigger or lesser degree. I'd say that between the free ones, Solaris is the closest you can get. BSD's are near enough, and Linux is different enough. There are many more.

Ubuntu is just a distribution of Linux, which has a Linux kernel and a lot of -mostly GNU licensed- tools that together build an OS. There are many more of these as well.

As for the differences between the tools, well, most UNIXes use either the original posix tools or at least tools of their own that are compatible with the original posix ones.

Most GNU tools -which are what linux uses instead- are a superset of the functionality of the original equivalent posix tool, but in any case they retain the posix compatibility as a subset because that's what any long-lived script will expect. That's done that way to retain portability between different unix clones. And of course, that also eases the life of the regular user when dealing with the command line. It's just easy to work when the tools always work like you expect them to.

When reading a man page in linux you will often find comments about the original posix functionality and behavior, about parameters that are even retained with no real functionality just for the sake of compatibility, and about GNU extensions which might not work on other UNIXes that use the posix toolset.

There are many unixes that can be used as personal desktops, but I usually just advice to go linux for that. Even today, the hardware support (overall the the newest technologies) is far better and comes much sooner into the linux kernel.

In which regards regular programs, most of the userland software is ported soon enough, a big part of it is developed with both OSes in mind and might even be released at the same time for both. Still some thing might lag behind.

Well, the pre-requisite to qualify to be a linux distro is to use a linux kernel. BSD's do have their own kernel, which are built from the ground and have absolutely nothing to do with the linux kernel.

I just see them all as a galore of clones of the original UNIX, linux relates less closely, BSD's relates more directly, and Solaris and some other commercial unixes relates even more closely.

However, I am admittedly no expert in either solaris, bsd's nor any other unix clone. I've only used them in the university as a user, and not as an administrator. So someone might have a different opinion about that.

In any case, as said, bsd's have absolutely nothing to do with linux, at all.

purest UNIX operating system
 

Thanks to all for this.

i92guboj - I'm beginning to get a better understanding of this from your post.

The whole history of this is quite interesting really and at least as users, we are now spoilt for choice on free software, and can try out and assess the various operating systems on virtual programs before installing.

Yep. That's true.

The thing about linux (which is maybe why it's more famous and extended than others) is that it's a very generalist OS. It can do lots of things very well and lots of things acceptably, while supporting the majority of the hardware available to one or another degree. This is what desktop users expect from a modern OS.

Other UNIX clones are maybe less generalist, but can do some things better (or at least, some people think so). BSDs are commonly named because of their security and stability. But even amongst BSDs you can find very different models. OpenBSD for example is centered about these principles of stability and security. Others like FreeBSD are more generalist, while still offering many of the advantages of BSDs in general. NetBSD instead has the advantage that it runs on a wide range of architectures, from huger server machines to some embedded devices. Linux can do all of this without a problem, whether it's good enough or not, better or worse or whatever else... that's open to discussion as always.

Solaris is UNIX
BSD is UNIX
Linux is UNIX

As was mentioned the purest /1st was AT&T. BSD came along shortly thereafter.

Any of these OS's will carry with them the core UNIX command set. So you can learn the basics from any of them. I can see where it would be hard to know that rpm's were not a original part of UNIX but awk was. To me RPM's came along to make things easier to install and update software with the proper versions so that things worked together. Nowdays things are so interdependent that things like dependencies have to be taken into consideration much more than 30 years ago.

Before Linux I worked on AT&T, HPUX, SUN-OS, Solaris and AIX. If you can work on one you can work on any of them. They all have their home grown goodies but the core commands are the same. Most of these core commands exist on all flavors of Linux. IMHO Solaris is no more pure than HPUX or AIX or Red Hat Linux / CentOS etc. Pick one. I really don't think you can go wrong. The better you get to know any one flavor it will make it that much easier to learn any UNIX derivative.

ps. I saw some AIX servers for 60 bucks on Ebay that came with the AIX OS. Cheap way to learn UNIX with a little of IBM's tidbits tossed in. (AIX is IBM's UNIX flavor).

purest UNIX o/s
 

Good - at least the fact that I'm learning Linux commands and operating systems will help if I ever trial the bigger UNIX.

From what I can see Open Solaris tales 500MB RAM at idle, which is too much for my laptop at the moment, unless I upgrade. I want to be running max 350-400MB at idle. Ubuntu's very conservative at <200MB at idle.

BSD looks good to experiment with, but the installation procedure is a test in itself and not at all user friendly. However, it has very small RAM & HDD requirements, so I'd probably be after a low footprint application.

For a low footprint OpenSolaris based distribution, you may want to try milax: http://www.milax.org/

purest UNIX
 

Thanks- I'll give this a try...

No actually Linux is a unix-like operating system. BSD was derived from the original unix implementation but Linux was a separate independent implementation

I'll add more =)
*BSD comes from 4.4BSD - UNIX
Solaris and SunOS are UNIX
HP-UX is UNIX
AIX is UNIX
IRIX is UNIX
OS X, born of Darwin born of born of NeXTSEP born of Mach born of 4.2 BSD, is UNIX

Simplifed timeline (Warning, big image).

Solaris is a registered UNIX product, conformant to the Single UNIX Specification (UNIX 03) standards.
Linux and *BSD are compliant with a lot of standards, but it costs money, etc. to have something registered as even POSIX-conformant, and POSIX is only a part of the larger Single UNIX Specification standards.
Linux and *BSD, in any documentation or anything, will be referred to as a UNIX-like operating system.
Solaris is UNIX
AIX is UNIX
HP-UX is UNIX
etc.
OS X (as of Leopard, I don't know if they were before) is using a lot of FreeBSD, and the Mach microkernel. It is a registered UNIX product, conformant to the Single UNIX Specification (UNIX 03) standards, just like Solaris and AIX, and HP-UX, etc. Mac OS X Leopard uses a lot of FreeBSD and also GPL'd software ... they have a modified version of gcc, etc.
CNET - Apple being sued by The Open Group
The Open Group
Register of certified products
Apple page mentioning features of OS X.

I don't remember who made the sarcastic remark, "The great thing about standards is that there are so many of them." This is true about Unix standards as well.
There are a number of functions, such as getconf, pathconf, fpathconf, sysconf which can help in sorting out the mess.
Two different Unix OSes can vary more in some areas than a "Real" Unix and Linux.

Here's the soap...

In the mid-1970's (heh... I was there...) the MULTICS project was a spectacular disaster, of the sort that only a government committee could produce. :) And so, a bunch of Bell Labs folks who just happened to have a PDP-7 on their hands decided to see what they could do with it. They came up with a little toy of a system they tongue-in-cheek called "Unix." (Multics...Unix... get it?)

Because AT&T was at that time a government-run monopoly, they had to release the source-code of Unix. So they did.

Fast-forward twenty years to a college kid who's freezing his butt off in Finland while hacking operating systems. To keep himself warm, he decides to build "a little x86 OS of his own." And he releases that source code to a Usenet news-group.

The system that Linus Torvalds bases his work upon is Unix ... but, having none of the source-code to the actual Unix system he works instead on a "fairly 'toy'" implementation of the POSIX standard. He employs a rather stunning collection of software tools, called "GNU," which had been pioneered by another rather amazing hacker, Richard Stallman.

And... it just happens to be "the right thing at the right time." From this tiny germ of an idea, and with the combined efforts of literally thousands of engineers throughout the Internet, a very full-featured operating system is created. It isn't Unix, but it follows closely in that system's footsteps.

As time goes on, "the dragon has eaten its tail." Engineering is like that sometimes.

AT&T was a monopoly, but not government owned. Due to an anti-trust ruling, they were not allowed to sell an operating system. So they developed Unix at Bell Labs for in-house use, to process patent applications. Because they couldn't sell it, they gave it away to some Universities. Because of the variety of main frames and mini's in use at the time, even propriety software was sold in source code form. When AT&T was broken up, the prohibition against selling operating systems was lifted, and Unix became a commercial propriety operating system.

Unix was not just used internally or by universities before AT&T was broken up. Several commercial proprietary operating systems based on Unix version 6 and 7 code were already sold in the late seventies and early eighties.

Linux is not based on Unix at all, as many folks tend to think. (lack of technical knowhow, and media influenced that are wrong)
Linux is based on Minix, which is on itself based (partly) on Unix.
So, linux is the so called third generation of the family of Unix, but not a direct member, that is minix.

You need to clearly define "based on" with such statements.

If "based on" means "based on concepts from ...", Gnu/Linux and Minix are both purposely based on Unix by design.

If "based on" means "based on code previously written in ...", Gnu/Linux, Minix and Unix are independent of each other and share nothing in common.

If "based on" means "was originally coded on machines running ...", then Minix was based on Unix, the Gnu stuff was based on Unix and the Linux kernel was based on Minix.

Minix isn't a direct member as you wrote, perhaps are you confusing with BSD which has its roots in Unix code.

This is what i ment indeed. And since linux is strict speaking the kernel only, it's based on Minix. (thus not Unix, strict speaking) :-)

teebones ...
You're saying that if something is "based on" Unix, then it's Unix ... If something isn't "based on" Unix, it isn't Unix.
It's all "based on" Unix.
FreeBSD is not recognized as UNIX. It is not conformant to the Single UNIX Specification (UNIX 03) standards. The official FreeBSD site refers to it as a UNIX-like operating system.
This is a quote from the freebsd.org about page, found here:
^"derived from BSD"^
This is a quote from the official Minix site:
^"UNIX clone"^

Apple's Mac OS X is a registered UNIX product (Single UNIX Specification standards, UNIX 03). It is "based on" the Mach microkernel and FreeBSD, along with other things like a modified gcc, for example.
Look here. Quote:
Not UNIX 03, but POSIX compliance is very widespread. FreeBSD, Linux, etc. POSIX is part of the SUS standards.
The Mach microkernel is also "derived". It's not UNIX.
The "not-recognized-as-UNIX" Mach microkernel and "not-recognized-as-UNIX" FreeBSD components, along with modified gcc, and other GPL'd software, and whatever Apple's done with them, make up a "recognized-as-UNIX" operating system. Today.
The fact that FreeBSD is derived from UNIX doesn't make it UNIX. It's not pre-standards UNIX, either.
Today, POSIX and SUS standards are used to recognize UNIX products. POSIX standards are part of the SUS standards. You can find POSIX compliance in everything. Also, the fact should be mentioned that GNU Hurd uses Mach.
http://en.wikipedia.org/wiki/POSIX

Also, I've read about today's UNIX operating systems. Moving from one to another can cause you headaches, and they're UNIX - standard UNIX - SUS UNIX 03 standards conformant UNIX operating systems.

Unix official conformance is moot for the rest of us. Most mainstream Unix, Unix like (read Gnu/Linux) distributions that do not officially comply would likely pass 99%+ of the tests.

Moreover, these standards are aimed to developers whose goal is to write portable code and scripts, not to admins or end users, not that much to the majority of software developers who usually only care of a limited set of OSes.

That's the reason why moving code, admins or users from one distribution to another is often painful.

I agree ... I care about the standards as much as I need to care about the standards, but I wouldn't make a decision about whether or not I like an operating system based on whether it's a registered product of some kind. Not taking price into consideration, I wouldn't personally buy Apple rather than use Linux. Linux is a very, very good operating system to me. If I wanted something "more UNIX" - which I think is a silly thing to worry about, really, especially when you can't make up your mind about what being "more UNIX" even is - I would use a *BSD or OpenSolaris or a commercial Unix of some kind. Going by everything I've read about this subject, there isn't "A UNIX" any more. Even all the registered UNIX operating systems like AIX and HP/UX aren't the exact same, it's just what they have in common.
Linux and UNIX have much more in common than a lot of people act like or think they do.
http://www.fas.harvard.edu/~lib215/r...inux.unix.html

From "Linux in a Nutshell", published by O'Reilly:

From IBM (who makes AIX, a registered UNIX operating system):
http://www.ibm.com/developerworks/ai...difflinux.html

Also, from kernel.org:
:p

Don't forget that the Open Group charges handsomely for testing and declaring a product "compliant." (You're talking thousands and thousands of dollars on a regular basis.)

For that reason, you're not going to see Linux distributions declared UNIX '03 compliant for a long, long, time . . . or ever, most likely.

Companies like Sun, IBM, and Apple have the extra cash to throw at obtaining a name. Since Linux is free, and, despite the nuances of its licensing, exists essentially in the public domain, no profit-motivated company has any compelling reason to pony up the hefty monies required to get it certified.

Even companies like Red Hat and Novell, who sell Linux and Linux support commercially, have almost nothing to gain from such a certification. After all, their customer base, and specifically the component of their customer base influencing the purchasing and usage decisions around their products (sysadmins, network engineers, etc) are all savvy enough that they already understand how Linux will fit into their infrastructure, regardless of what it is or can be legally called.

It's clear that we are all just traipsing around semantics only made necessary by intellectual property rights on a name that somebody owns and keeps getting sold.

That's why we always have to say, "of course, Linux isn't really UNIX (wink wink)."

I mean, come on, the very fact that you have to say that Slackware and FreeBSD are not UNIX, but MacOS X is demonstrates how laughably meaningless the label of UNIX imposed by the SUS has become.

Run Solaris, run AIX, run HP-UX, then try migrating to Slackware or FreeBSD. After you are done, migrate anew from those other real UNIXes to MacOS and tell me which migration was more seamless.

You probably don't even have to do it to tell me the answer.

It is also worth noting that UNIX has evolved FAR beyond the System VR4 days, even the directly-derived versions like Solaris. AT&T System VR4 would not meet the Open Group's SUS.

There is one great point in this thread with which I feel that I should qualify this answer:
That being said, one would have a hard time finding incidences in which code written for SUS-compliant operating systems would not port to Linux, and probably an even harder time with FreeBSD.

(FreeBSD was originally derived from 4.3BSD-Lite, which was the actual, honest-to-God, AT&T UNIX-descended version of BSD, just stripped of any AT&T code that had not been re-written yet.)

I just have to say this to satisfy my own desire, as I haven't had any opportunity to before, so I apologize: I friggin' love FreeBSD . . . I think it is just about the best free OS for a server machine. I have to say, though, that I can't imagine anything other than sheer nerdiness which would motivate someone to use it on their desktop. (Not that there's anything wrong with nerdiness . . . but a FreeBSD desktop? Now that is some hard-core nerd style.)

Summarizing, Linux may not be UNIX, but you could, speaking out loud, call certain distributions of it like Slackware, Red Hat Enterprise Linux, and Suse "you-nicks" and be correct. :)

Hence the handy contraction *nix, although its unpronounceable unless you like saying star-nix or (worse) asterisk-nix :( ;)