Why do people say “unix” or “Unix-like” instead of POSIX
Posted by Lopsided-Cost-426@reddit | linux | View on Reddit | 224 comments
The term “POSIX” seems far more useful, it’s used to talk about OSes that conform to the POSIX standard something that is very specific whilst “unix-like” seems far more subjective and “UNIX” could refer to the OS.
NursingHome773@reddit
because no one cares
flecom@reddit
does anyone under 40 even remember that unix was a thing?
HighLevelAssembler@reddit
Was a thing? It still is a thing.
flecom@reddit
unix is still a thing? where? and I don't mean unix-like, IOS is not unix, HPUX is basically dead, ATT unix? lol
HighLevelAssembler@reddit
IBM AIX is still used heavily at big enterprises. Think banks, insurance, other kinds of financial institutions. If they've got a mainframe, they've also probably got some POWER systems running AIX.
flecom@reddit
funny you mention that, I just installed AIX on an itanium system because I hate myself and do these things for fun
plus I am old so I do remember unix was a thing :)
Irverter@reddit
A dying thing. The only Unixes that aren't discontinued are macOS and AIX.
Positronic_Matrix@reddit
There will be more Unix operating systems shipped in 2026 than any other time in history and that’s simply counting macOS, iPadOS, iOS, and watchOS. Beyond that there is AIX, HPUX (still maintained), z/OS, UnixWare, and Open Server.
Realistically one must also include all the GNU distributions as well, given that it replaced most of the commercial offerings.
In 1995 the installed UNIX base was in the millions. In 2025 the installed UNIX and GNU base are in the several billions. Saying unix is a dying thing is absurdly wrong. There are more Unix ingratiated shipped in a day in 2026 then there was in a year in 1995.
Irverter@reddit
Which are basically the same. iOS rebranded and with a UI fitting the device. By the logic Debian with GNOME and Debian with KDE are two operating systems.
Discontinued. On extended support.
Forgot about those. Though OpenServer latest release was almost 10 years ago.
Which are unix-like, not Unix.
Positronic_Matrix@reddit
Of course they are the same, so let’s count every seat. That said, let’s throw out HPUX, let’s throw out UnixWare, let’s throw out OpenServer, and let’s throw out GNU.
The installed Unix base is still several billions. Unix is at its peak right now.
Irverter@reddit
Ok, so I've been talking about the amount of Unix OSs, while you think I'm wrong because you're talking about the amount of devices running a Unix OS?
Positronic_Matrix@reddit
Whee! I guess we’re both right. :D
AnonFur1996@reddit
Dude. You can't imagine both are right when you're the one wrong.
Positronic_Matrix@reddit
Imagine being so prideful you deploy a sock puppet account with a dismal -8 comment karma to get you through the pain of being dunked on. 🤣
Irverter@reddit
Thinking you're right because you're discussing something different to the actual discussion isn't a "pleasant" outcome at all.
Positronic_Matrix@reddit
I won’t hold it against you.
just_posting_this_ch@reddit
Vast bulk of the things you describe are not referred as unix. As per links in this section, they might not even classify as unix, but that is beside the point. In 1995 you could walk into a computer lab and use "Unix". Right or wrong it was a pretty common term.
Hail_CS@reddit
i used to work for a fiber optics telecom company about 2 to 3 years ago. I was a C systems programmer and we had to ensure our code would compile on a whole lot of different systems, which included not only the major linux distributions, but also HPUX, SunOS/Solaris, and AIX. a lot of the hardware responsible for operating the fiber optic networks in the country run Unix systems, which makes sense as Bell Labs, where Unix was created, was owned by AT&T.
HighLevelAssembler@reddit
Those are the only branded Unixes still around, and complying with that standard is more of a box-ticking exercise for vendors trying to land government contracts. There have been UNIX-certified Linux distros in the past. Linux, the BSDs, and AIX are more alike than they are different. They're all Unix, they all share some genetic lineage back to Bell Labs and Berkeley, especially in userspace.
Irverter@reddit
Which is what I said. Not unix-like, unix-based, unix-inspired or any other term that includes beyond Unix.
Secret_Conclusion_93@reddit
Yes, people who wonder why Mac and Linux are similar in terms of terminal usage might search the reason.
Especially if coming from Windows.
flecom@reddit
so linux is unix? got it
Lopsided-Cost-426@reddit (OP)
It’s not even a matter of being technically correct it just seems like POSIX would be more useful in a casual conversation
mckenzie_keith@reddit
Windows NT was posix compliant. Do you think there are a lot of people out there who, when they say unix-like are intending to include windows NT?
algaefied_creek@reddit
HaikuOS derived from BeOS as well.
Also Windows Terminal with Powershell with MINGW64 and other POSIX shells, and WSL2.
That hardly makes Windows 11 in that category either
poudink@reddit
BeOS was neither Unix-like nor POSIX compliant (and by extension neither is Haiku), so it isn't relevant here afaik.
algaefied_creek@reddit
Haiku has had a POSIXy libc but was missing some critical extensions. To fix that:
HAIKU OS: THE OPEN SOURCE BEOS YOU CAN DAILY DRIVE IN 2024
Their POSIX 2024-compliance work is ongoing but is quite advanced in its completion.
dannyvegas@reddit
Windows 11 isn’t. Windows NT and Windows 2000 were FIPS 151-2/POSIX.1 certified at an API level in order to meet government requirements
borkyborkus@reddit
Seriously, this debate is the kind of thing that keeps new users away. I can’t believe how much it’s talked about compared to how infrequently it’s relevant to the user experience.
fraxus1@reddit
POSIX takes all that 1980s era goodness in software and preserves it in amber like a museum piece. So it is unable to morph, change, iimprove and evolve. There are a lot of good reasons why an OS should not be POSIX compliant, there are only a few valid reasons for requiring posix compliance.
Over_Dingo@reddit
https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem
Windows, the newest Unix-like
realguy2300000@reddit
because almost nothing is actually 100% posix compliant , and even less is formally posix certified.
JustBadPlaya@reddit
MacOS is the only mainstream POSIX-certified OS I believe
spyingwind@reddit
macos, solaris, and z/os are certified.
doubled112@reddit
Are Solaris and z/os mainstream?
Balcara@reddit
I'm certain you would be very upset if z/OS ceased to exist suddenly. Perhaps more so than if Linux stopped existing.
NathanTheGr8@reddit
lol no. Both OS are used by businesses but a lot more shit would break if Linux disappears. By at least 2 orders of magnitude. Almost every place running a mainframe has Linux boxes or vms many more places in the stack. The same isn’t true the other way around. Does Google, or Facebook, or was use mainframes? I doubt it is possible to get reliable stats on zOS installs. You could prob extrapolate from ibm revenue.
Pale_Height_1251@reddit
A lot more stuff would break, but much of it trivial. Would you rather lose banking or Faceybooks?
NathanTheGr8@reddit
banking would also break with the loss of linux. You think banks only run mainframes? hell the mainframes themselves often run linux as a guest OS.
deltwalrus@reddit
lol yes. If Facebook or Google lost Linux suddenly it would be a shitshow (maybe not Facebook…) but without z/OS, literally the entire financial transaction backbone of America and much of the western world would collapse. Credit card transaction? Hits a mainframe every time, guaranteed. Booking a flight? Managing large supply chain inventories?
Linux servers can be easily and quickly replaced in a disaster. Have been many times. Mainframes have oodles of nines for many good reasons.
Temporary_Pie2733@reddit
It would probably be easier to replace Linux with some flavor of BSD than to replace z/OS with… I’m not even sure what the closest analogy would be.
Balcara@reddit
Not sure how anyone would be able to pay for anything though? Society would collapse, and that's not an exaggeration.
CirkuitBreaker@reddit
Most banks and card processors use mainframes. So losing z/OS would be much worse.
bawng@reddit
Mainframe mainstream
froli@reddit
Mainframe itself is not even mainstream.
qb45exe@reddit
You’d be surprised
froli@reddit
I know they are still around and that there's plenty of them still. That's different than mainstream though.
Thebombuknow@reddit
I think something is only mainstream if you could a random person on the street could tell you they've heard about it, without you getting lucky.
Most people have at least heard of macOS.
hidazfx@reddit
all of the FIs I’ve worked for have ran on their core banking solutions on modern IBM mainframes
eo5g@reddit
Holiday inn
JG_2006_C@reddit
So openSolairs(Ilumos is posix? Cool guess that helps)
natermer@reddit
It doesn't mean a whole lot.
A couple versions of Microsoft Windows NT was certified POSIX.
It is mostly obsolete nowadays. The standard for binary compatibility between Unix-like systems is "Linux compatibility layer".
ldn-ldn@reddit
Not couple, up until Win10.
JustBadPlaya@reddit
The line between "mainstream" and "relevant" is thin and I shall not dare to draw it for mainframe OSes
tux-lpi@reddit
macOS is Unix, and mostly POSIX compatible (with some versions certified, and some versions lacking newer standard POSIX features).
Linux is famously Not Unix, and also mostly POSIX compatible, but intentionally not 100% and not certified.
Rodot@reddit
Technically, it's GNU that is famousy not Unix
Positronic_Matrix@reddit
What does GNU stand for?
nijou8024@reddit
GNU is Not Unix :)
xtifr@reddit
MacOS also got certified as an actual Unix™. Which is a much more detailed and precise standard to meet!
iamapizza@reddit
It's a "well yes but actually no" - https://www.osnews.com/story/141633/apples-macos-unix-certification-is-a-lie/
Positronic_Matrix@reddit
This is incorrect. macOS is an officially certified UNIX operating system. It is built on Darwin, an open-source, BSD-based UNIX system, and its core, known as the XNU kernel, is a hybrid of BSD and Mach. While it runs a proprietary interface, it fully complies with the Single Unix Specification.
RoomyRoots@reddit
Didn't they not renew it some versions ago?
corruptbytes@reddit
Tahoe is certified it seems
https://www.opengroup.org/openbrand/certificates/1223p.pdf
Haunting_Swimming_62@reddit
And it's not even compliant (timespec shenanigans)
ilep@reddit
There is AIX from IBM, HP-UX and Sun Solaris have been certified as Unix-compliant, along with macOS. That is basically just a paper saying that it passes some tests and can use the trademark.
I don't think there is anyone doing Posix-certifications.
Ok-Buy5600@reddit
It's not just "passes some tests". It means it can execute whatever is made to be executed on linux.
atomic1fire@reddit
Posix is a certification built around Unix.
Linux happens to copy Unix behavior with a best effort so there's some level of Posix compliance but it's not perfect.
But for the average user I don't think Posix compliance means anything, and if it is a requirement you could just buy a Mac.
ilep@reddit
Not really, API-level is different from ABI (binary compatibility) as there are different processor architectures etc.
algaefied_creek@reddit
Haiku contains POSIX-like features for its shell; but the kernel is nothing like UNIX, for example.
mykesx@reddit
Doesn't Windows have some posix compatibility, too ?
stiggg@reddit
It had from the first version of NT on, but it was removed in Win10 where they later added WSL
thunderbird32@reddit
The POSIX layer was just to tick a box on government procurement requirement forms. At least early on it was almost entirely useless and got worse over time. https://virtuallyfun.com/2026/04/19/fun-with-posx-subsystem-on-nt/
Tall_Decision_6516@reddit
Like ISO 9000?
Tall_Decision_6516@reddit
Like ISO 9000?
SpeedDaemon1969@reddit
Windows had a POSIX layer, just like it had an OS/2 layer. The POSIX layer didn't do anything without special, extra-cost software however. With the OS/2 layer it was possible to run 16-bit OS/2 executables on Windows NT.
amackenz2048@reddit
It's why NTFS supports symbolic links IIRC...
SpeedDaemon1969@reddit
Yes, NTFS has some odd features that hardly ever get used. It also supports multiple streams, so in theory it can handle resource forks that old Macintosh files used. I don't think anyone has used that feature, but it would be ideal for ad hos steganography of sorts.
ludonarrator@reddit
Alternate Data Streams are used by the ntfs-3g driver on Linux to store extended attributes. And xattrs are used for some common things, like tagging files (
user.xdg.tags).codeasm@reddit
Ow rings a bell,think some exploits used these to trick to become system. Not sure if the multiple streams was the issue, probably the way the kernel handled being given another alternative things to read
SpeedDaemon1969@reddit
AFAIK the only programs that can even use NTFS streams were written by Mark Russnovich and released as streams.exe in the SysInternals suite. I don't know about any exploits through it, but you can use it to hide a text file (say, with a password) in some other data file on a Windows computer.
webtroter@reddit
There's also the Zone.Identifier "file" that indicates that the file was downloaded from a remote location.
codeasm@reddit
Interesting 😎 also the replies.
Googled a bit: libgit2 https://www.wiz.io/vulnerability-database/cve/cve-2020-12278 Winrar https://www.seqrite.com/blog/winrar-directory-traversal-ntfs-ads-vulnerabilities-cve-2025-6218-cve-2025-8088/
Thus, usefull, cool feature, but also tricky if not aware of when developing software that talks to ntfs based fs. Cool. Thanks for the answers all
adzm@reddit
What, all you needed to do was add a :streamname to the file name. It is still used to add metadata to files, most commonly to files downloaded from the Internet so they have extra safety measures when used.
lainlives@reddit
It's used for system restore, many antiviruses make use of it for various functions. And 'file versions' is a feature i used to enable in windows, would let me roll back any file. Wasnt until btrfs I had a setup that clean in linux.
QBos07@reddit
Most notable use case is the RegionZoneIdentifier wich make the „this file is from the internet“ warning. And directories are implemented using them.
Portbragger2@reddit
yeah afaik NTFS is posix compliant but ironically not on windows hosts :)
Mordiken@reddit
Actually, that's something pretty neat about Windows architecture: It has no "native" userspace API because userspace APIs are implemented as "personality" subsystems and a single system can run programs targeting the different the supported APIs simultaneously.
Back before WSL was rewritten as deeply integrated VM running the Linux kernel, WSL1 was actually implemented as proper windows subsystem based on Windows Services for Unix which operated alongside and at the same level as the Win32 API as another supported API...
So, technically, if Microsoft wanted they could have turned Windows into GNU/NT.
Admirable-Safety1213@reddit
M$ makes stupod and anti-technological decisions but Windows paradigm while not very UNIX and many ways Anti-UNIX its very interesting
Mordiken@reddit
MS is actually a textbook example of a phenomenon Steve Jobs described in a interview.
Once a tech company achieves a dominant market position, further growth can only happen through sales and marketing, which leads to sales and marketing people being promoted until eventually they end up displacing most of the product and engineering people from the executive positions within the company, and when that happens the product genius responsible for putting the company in a dominant position in the first place gets "rotted out" of the company.
And that's why Windows has been on a downward spiral ever since the debut of Windows 8, which was actually the very first Windows release to be entirely driven by sales and marketing execs having a panic attack over the iPhone and iPad.
techman2692@reddit
Not saying Bill was a factor in that, but he left around that time for retirement, in addition to a slew of other changes happening at MSFT at the time.
ArdiMaster@reddit
The chief architect of NT, David Cutler, famously hates Unix.
Albos_Mum@reddit
Windows will never go anywhere until Microsoft finally releases Services for TempleOS.
linuxhiker@reddit
Yes
Idontknowichanglater@reddit
Haiku’s userland feels pretty POSIX-inspired, especially the shell environment, but the kernel itself is its own thing and not Unix-derived in the traditional sense
so it ends up being “Unix-like experience” on top without actually being Unix under the hood
algaefied_creek@reddit
Yeah that’s actually really cool. Just noticed they are aiming for POSIX 2024 compliance
gordonmessmer@reddit
POSIX doesn't dictate how the kernel works, only how the user-space works.
natermer@reddit
This is 100% correct.
POSIX is essentially a standard for writing OS APIs. It dictates a standardized set of system calls, OS utilities, and other related things with the goal of making portable software easier to write.
It doesn't dictate OS design, though. It doesn't prescribe how the kernel works, how the init system is designed, or other features that go beyond what POSIX requires.
knucklehead_whizkid@reddit
QNX is like that as well, in the sense that it's POSIX-compliant but the architecture internally is nothing like UNIX (or even Linux). In fact, for most embedded systems trying to have your application use POSIX APIs can sometimes be worse for performance than using the QNX ones
algaefied_creek@reddit
Very true!
ExternalUserError@reddit
Also Microsoft Windows is pOSiX coMpLiaNt.
ready_or_not_3434@reddit
Yeah, POSIX is a rigid spec but "Unix-like" is basically just shorthand for the practial dev experience. If it has standard pipes and a decent shell, people are gonna call it unix-like regardless of any certification.
RolandMT32@reddit
I think "unix" and "unix-like" are more recotnizeable terms. Also, as some others have said, not everything is 100% POSIX-compliant (and maybe nothing is). For instance, Haiku OS (based on BeOS) looks & feels like Unix, but it's not totally POSIX-compliant (and I don't think it was initially designed to be).
Teru-Noir@reddit
Bc linux is a unix clone
0jdd1@reddit
They mean very different things! A UNIX™ system derives from Bell Labs UNIX, which still means something. A POSIX system is anything someone has slapped a “POSIX” layer on top of for marketing reasons. A UNIX-like system could be something like Linux, which comes close, or it could be something I’ve cobbled together in my garage, so that doesn’t mean much at all.
__mson__@reddit
Back in the day we used to call it *nix because of lawyers or something.
Sataniel98@reddit
They're fundamentally different things. You don't need to be Unix-like to implement the POSIX standard. Any OS can do that. VMS does, early Windows NT did too. Calling Linux Unix-like also contains more information because it highlights that Linux in fact doesn't stem from Unix.
TheBendit@reddit
Windows NT was properly POSIX certified. This was necessary in order to be allowed to bid on certain government contracts.
myrsnipe@reddit
It was POSIX certified, but in reality it was barely working
Sataniel98@reddit
Oh, it was definitely working, but not very well-integrated into the system. You could hardly have interactions between programs running in the POSIX subsystem and the Win32 subsystem.
thunderbird32@reddit
Maybe for some definitions of "working" but it was certainly almost useless as implemented:
https://virtuallyfun.com/2026/04/19/fun-with-posx-subsystem-on-nt/
ldn-ldn@reddit
The post is about NT 3.1. It was very useable during XP era. It was much better than CYGWIN.
TheBendit@reddit
Windows XP has Windows Services For UNIX, which is completely different technology. It was not POSIX certified, but it actually worked.
This is just another example of how POSIX certification is of no use at all, in the best case.
BitOBear@reddit
Just like docx is technically an open standard, but that open standard contains arbitrary binary blobs as an allowable component and so the binary blobs inside of docx are basically opaque and unspecified.
And Microsoft had to break the IEEE in order to accomplish that little feat. It's almost impossible to get things through the IEEE now because Microsoft got all these countries to join but they don't actually show up and so often times quorum cannot be reached or the mandated voting thresholds cannot be surpassed for proposed standards.
There are too many governments attached, or at least there were for a while I don't know if it's still true, and most of those governments don't care to participate they only showed up because Microsoft paid them to in the first place and Microsoft isn't paying them to vote on things that Microsoft doesn't care about.
orbvsterrvs@reddit
And they made it so complicated as a standard--the ISO-29500-1:2016 PDF version clocks in at 3,810 pages, if we include the Annexes it goes up to 5,033.
Easy reading for developers of word processing software. All you need to be compliant is this one ISO standard! /s
o462@reddit
Always has been... and still the case.
TheBendit@reddit
Exactly. POSIX certification is very expensive and also useless except if your customers demand it.
If important enough customers demand that you get a priest to pray over your product, then you arrange for that to happen. It is good to be that priest.
AliOskiTheHoly@reddit
It stays funny to me how MacOS is certified UNIX but Linux is forever stuck being UNIX-like because the developers could not give a fuck paying money for that certification when it could be better spent paying developers.
algaefied_creek@reddit
Indeed, it’s a MINIX-like re-write which itself was a pedagogical UNIX-like clone?
georgehank2nd@reddit
It's not a rewrite of MINIX (or anything else for that matter).
do-un-to@reddit
Read again. They didn't say it was a rewrite of MINIX.
But they did in fact say it was a rewrite, and you're right that that's wrong.
Linux, IIUC, was a de novo creation of a unix-like, POSIX-aspiring OS, with inspiration from and a lot of modelling on MINIX, yet with substantial changes, and a lot of adoption of GNU userland (though I'm unclear how much was wholesale incorporation versus more indirectly being modelled on GNU).
RangerNS@reddit
Linux proper is just the kernel. When initially developed, it replaced the MINIX kernel, still using the MINIX userland.
Others - not Linux - were responsible for bundling the GNU userland with the Linux kernel into a "distribution". And these distributions pulled in software from all over the place, not only the gnu project.
do-un-to@reddit
Linux is at least a couple things. What people generally refer to these days is the kernel itself or to "distros" based on the kernel. In its earliest days, I believe for the first iterations, he talked about it as an "OS", and mentions its "file-system".
I couldn't find information about it replacing the MINIX kernel. I did, however, find an FTP server with some really old Linux downloads. We could figure out exactly what was what there, I think.
In short, it seems still that Linux was an OS, not just a kernel, before distros existed.
Clearly now the Linux kernel is the wellspring of everything Linux (and much beyond), and the most fundamental thing to focus on, sure. Whether that's "proper" Linux depends on how you define proper.
TheBendit@reddit
It was wholesale incorporation of the various GNU tools for many years. Back then you would often install the GNU tools even on commercial Unices, because the built in tools were generally limited, slow, and buggy.
Sataniel98@reddit
I don't think you can call it MINIX-like. Minix was an inspiration of some sort, but they're architecturally very different (at least, beyond the shared Unix similarity). (In-) famously, Tannenbaum and Torvalds debated about micro kernels vs. monolithic systems.
FatBook-Air@reddit
I was gonna say, I distinctly remember Microsoft going down the POSIX standard road. When I discovered that was when I began to question what it actually meant to be POSIX compliant.
the_humeister@reddit
There's also UNIX certification, which some versions of Mac OS X did get, even though the kernel runs XNU (i.e. Xenu is not Unix).
thephotoman@reddit
Every version of MacOS since 10.4 has held Unix 03 certification.
The kernel does not “run” XNU. The kernel was once named XNU. It has been called Darwin for a while now, though.
Positronic_Matrix@reddit
This is so inaccurate it’s causing me pain. macOS is built on Darwin, an open-source, BSD-based Unix system, and its core, known as the XNU kernel, is a hybrid of BSD and Mach. While it runs a proprietary interface, it fully complies with the Single Unix Specification.
the_humeister@reddit
The kernel is still called XNU. The entire open source OS that macOS utilizes is called Darwin.
sogun123@reddit
POSIX is attempt to standardized UNIX like systems, or not? There was UNIX, people forked it, cloned it and diverged. POSIX tried to bring divergence to some common api. But the origin and idea is still UNIX, so we go for Unix-like. Or it is just custom :-D Actually, POSIX itself was influential, but by itself it failed i think. But I guess it ended up bit better than sql
dgm9704@reddit
Because windows is/was POSIX also?
Positronic_Matrix@reddit
Windows 11 is not POSIX compliant.
Morphized@reddit
It can be if you install a third-party subsystem
dgm9704@reddit
no but Windows NT was
Lopsided-Cost-426@reddit (OP)
Windows is not remotely POSIX compliant but there are comparability layers.
j0nquest@reddit
Windows NT shipped with a posix compliant subsystem, alongside Win32 and OS/2.
Positronic_Matrix@reddit
Windows 11 is not POSIX compliant.
Windows NT was released in 1993. Why is an OS released in 1993 being referenced here? I’m confused.
j0nquest@reddit
No one in this thread claimed windows 11 was posix compliant. The point is that posix means nothing for specifically identifying a family of operating systems. I could be talking about the first NT release or some other not-like-unix at all OS that bothered to get a posix certification. That’s why people talk in more specific terms than just saying posix. Posix compliance is a feature any OS can strive to support. That’s it, nothing more.
Positronic_Matrix@reddit
I appreciate the clarification. We are in agreement.
Positronic_Matrix@reddit
Windows NT was released in 1993. Why is an OS released in 1993 being referenced here? I’m confused.
Positronic_Matrix@reddit
Windows NT was released in 1993. Why is an OS released in 1993 being referenced here? I’m confused.
RangerNS@reddit
Your basic question is kinda silly for anyone in the know, but fair is fair, you don't get to know things unless people who do know things tell you.
Its a rather odd stance to ask questions of those who know more than you, and then immediately tell them they are wrong.
MorallyDeplorable@reddit
He's not wrong, though. Windows is not POSIX compliant and hasn't been for many years now.
RangerNS@reddit
/u/dgm9704 said "is/was"
Windows was POSIX compliant.
This says more about the POSIX standard and the process required to get something certified than it does about Windows. It helps answer the OPs basic question: Because even at the time being POSIX compliant was at all a vaguely useful line in the sand, it wasn't a very useful line in the sand.
MorallyDeplorable@reddit
If you actually think about it Windows was not POSIX complaint, ever.
It had a paid/expensive/relatively isolated posix compliant subsystem as an optional installable addon. It wasn't compatible with the normal win32 subsystem, you couldn't write a meaningful desktop app in it, you couldn't use it to control Windows or interact with it at large. Windows as an OS was never POSIX compliant, it just so happened that an addon piece of software existed that could create a POSIX compliant environment on Windows.
bigbearandy@reddit
The market moved faster than POSIX, so POSIX is no longer a selling point. It only really matters for the scripting and invocation portability of some common tools, like bash, grep, find, tar, and awk.
apex6666@reddit
I’ve genuinely never heard of POSIX
ChainsawJaguar@reddit
I use fish shell in my chosen terminal, Ghostty, and fish is most certainly not POSIX compliant in some ways. However, it's very Unix-like!
syklemil@reddit
Yeah, just as far as shells go, I think most of us prefer not to use a POSIX shell, instead opting for some shell that has various ergonomic features, either for interactive use like fish, or for scripting, like bash.
Actually writing scripts for POSIX sh means we lose out on nice features, and plenty of us have to rely on tools like
checkbashismsto not accidentally write something unportable that doesn't run on some simpler POSIX sh. Beyond Debian's use ofdashI'm not even sure how common it is to write for POSIX sh rather than bash in the Linux world.kudlitan@reddit
The simple answer is that Unix refers to the Single UNIX Specification (SUS) while Posix refers to The Open Group Base Specifications.
These are two different specifications that may overlap but not identical and maintained by different organizations.
Therefore Unix and Posix refer to two different things.
For what it's worth, Linux is neither Unix nor Posix.
sudogaeshi@reddit
*nix
/thread
Nevyn_Hira@reddit
They're describing different things.
daddyd@reddit
two different things, you can be posix compliant while not being a *nix OS.
lmarcantonio@reddit
POSIX is horribly outdated, that's the reason. There are newest 'standards' like the SuSv4 which are better/more complete (and actually an extension of POSIX).
I guess these day we talk about POSIX as "the standard thing", which is certifiable but you don't want to be certified because some choices are... questionable (the env POSIXLY_CORRECT gives and example of these)
markand67@reddit
do you know POSIX 2024?
lmarcantonio@reddit
Actually no, thanks for the pointer!
JG_2006_C@reddit
Find me a 100% posux complyant os🤣 mean some industral os ran by simens maybe😂
arf20__@reddit
Windows is POSIX compliant, somehow.
gerowen@reddit
Because even Windows is POSIX compliant. But it's far less Unix like than Linux or BSD.
Heyla_Doria@reddit
C'est comme ca c'est la vie des langues et leur usages. Il existe plein de concept qui n'ont pas vu l'adoption du mot le plus adéquat
Tu t'en rend compte ici car tu maitrise le sujet et tu tiens a le montrer....
markand67@reddit
english maybe
markand67@reddit
POSIX refers to a spec of common interfaces, conventions guidelines and utilities. Under the hood the operating system can be completely different than a UNIX-like kernel.
For example, UNIX philosophy refers often to simple/stupid. One process to do one thing. Nothing prevents you to do the opposite: utterly verbose command line, no "everything is a file" but still be POSIX compliant.
They are orthogonal.
yahbluez@reddit
posix is younger than unix, i guess the standard comes 10 years later.
Thick-Bug2634@reddit
I just say Linux. It's the new POSIX standard after all.
HelicopterUpbeat5199@reddit
I say "unix" lowercase because I want to say "not windows or mac and it is probably serving something and if I log into it I can probably run grep, vi and tar" and saying "unix" seems to do that job for me. And "Unix like" just doesn't roll off the tongue.
Yugen42@reddit
Linux is not Posix compliant
Leverquin@reddit
What is posix o.o
darkbyrd@reddit
Because they mean unix-like. Linux isn't POSIX.
LiahKnight@reddit
Because one is a computer interoperability standard, the other is an operating system.
neoh4x0r@reddit
Maybe because the original UNIX was not POSIX-based, that came about later.
Inoffensive_Account@reddit
Why do people say Tylenol instead of Acetaminophen?
kevin_k@reddit
Because they are two different things. Windows NT was technically "POSIX-compliant" but it wasn't Unix or "unix-like".
jimmcfarlandutah@reddit
Because no one would have a clue what you’re talking about.
the_latin_joker@reddit
POSIX is a certification you can buy, AFAIK Mac OS is POSIX compliant but Linux isn't since they haven't paid for it.
muffinstatewide32@reddit
Youre thinking of unix. You can get unix certified but you gotta pay
Posix is a set of standards. Surprisingly windows is posix compliant…. Or at least was at one point
EmberGamingStudios@reddit
There's non-Unix/Linux OSs with(or that had) POSIX such as Windows, VMS, and various others as POSIX is about portability, Unix or not.
Time-Transition-7332@reddit
have a look at Wikipedia, Linux is partially conformant with Posix, along with many other OS's
TheOneTrueTrench@reddit
Whatever you think POSIX means, you have vastly misunderstood what it is.
xtifr@reddit
I think their misunderstanding of UNIX is probably even greater! 😀
Ok-Winner-6589@reddit
The only Big OS with a POSIX certificate and POSIX compliant is MacOS. Linux and FreeBSD are only partially compliant and Windows isn't even close
Unix means that the software is a fork of UNIX, UNIX-like means being inspired by Unix (so at least partially following the POSIX standars).
Meanwhile when you say UNIX and UNIX-like you say that they (at least) partially comply with the POSIX specification (as it's based on UNIX)
Also nowadays we have newer standars mostly inspired by BSD and GNU/Linux (for example we have the standar File System Heriarchy and the XDG directory specification), so I find It a bit dumb to keep POSIX and UNIX, specially when people usually don't include Mac on UNIX and is eay more used than POSIX
xtifr@reddit
That has not been true for over three decades! The UNIX trademark was given to X/Open back in 1993, and ever since, any OS certified to pass the Single UNIX Specification (which replaced the earlier X/Open Portability Guide, or XPG) is officially a Unix, and any OS that is not so certified is not a Unix, no matter what its pedigree!
This is why MacOS is a UNIX™, but none of the BSDs are.
untamedeuphoria@reddit
Posix is a standard. Unix is a group of operating systems that adhere to the posix standard.
kombiwombi@reddit
Two reasons.
The first is correct attribution to the inventions and synthesis of Thompson and Ritchie. The family of operating systems used Unix as their guiding star. They did not use the work of the Posix committee in the same way. Bruce Sterling summed this up well in his quote that Unix is the foundational Ur-myrh of operating systems.
The second is accuracy. Claiming to be Posix compliant is to make a statement about formal testing against a specification. But to sidestep that and claim to be a Posix-like operating system is to allow many operating systems which are not Unix-like.
xtifr@reddit
Unix is every bit as specific as Posix! In fact, the formal Unix™ standard is much more precise and detailed than the Posix standard! However very few systems fully comply with either standard, so really it comes down to a choice between "unix-like" and "posix-like". And of those two options, "unix" is more likely to be a term people recognize! At least slightly!
Trivia note: MacOS is or was officially certified as passing the Unix standard, and thus not just "posix-compliant" or "unix-like", but an actual honest-to-god Unix™!
(Unix used to mean "descended directly from Bell Labs code", but the trademark was handed over to the Open Group over three decades ago, and ever since then, any OS can apply to be certified as Unix™. There was actually a version of Linux that was certified for a little while, but these days, really, nobody cares.)
HighLevelAssembler@reddit
Calling Linux "Unix-like" is pedantry to begin with. The "true" branded UNIXes are as different from each other as they are from Linux and BSD.
Linux is Unix. The BSDs are Unix. AIX and Solaris are Unix.
high-tech-low-life@reddit
I say POSIX regularly.
Rebootkid@reddit
I just say, "non-windows" because even non-IT people tend to understand.
ironykarl@reddit
I'm not disputing the Unix != POSIX arguments in this thread (cuz that'd be stupid)...
But a ton of commenters seem to not understand that POSIX mandates both a bunch of Unix APIs and the presence of Unix utilities (and norms regarding file systems, etc, etc).
Yeah, Microsoft pursued some half-assed POSIX compliance for NT in the past to try to make themselves eligible for government contracts, so you can definitely implement some amount of POSIX and still not have a usable Unix. But MacOS actually is POSIX compliant is a Unix.
One of the big issues here is that there are a number of Unix certifications, and (as others have said) a lot of Unix-likes haven't bothered to pass them
tslaq_lurker@reddit
Not even every Linux shell is POSIX
Yaya4_8@reddit
UNIX and posix are too different certifications
rcampbel3@reddit
Because being POSIX-compliant was all about paying money to a consortium and being officially cerifited... If it looks like a duck and quacks like a duck, it's UNIX. If it looks like a duck and quacks like a duck and has gone through a baroque commercial certification process, it's POSIX
ctnguy@reddit
Possibly because Linux, the most prominent Unix-like OS, is not actually POSIX certified (although it is mostly conformant).
TheBendit@reddit
Several Linux distributions are POSIX certified. For the most part no one cares.
funforgiven@reddit
I don't know any single Linux distributions that are POSIX certified at the moment and you know several?
TheBendit@reddit
You are correct, my information is outdated. The certifications have expired.
apathetic_vaporeon@reddit
Besides what others said, it’s just easier to write/say.
Technical_Rich_3080@reddit
Some distros of Linux are officially UNIX certified.
bombatomica_64@reddit
Posix is so bad as a standerd btw. Like everything in it is so bad to work in it (C neckbeard wet dream tho)
michaelpaoli@reddit
Various reasons, e.g.:
UNIX existed long before POSIX
Technically it's not POSIX unless certified so, so most stuff that would be more-or-less POSIX if tested for certification, technically isn't POSIX, as it's not certified so. And getting certified cost a non-trivial chunk of change, so most *nix isn't POSIX.
Wanna see what's actually certified, have a look here: https://www.opengroup.org//openbrand/register/
SpeedDaemon1969@reddit
UNIX and POSIX are completely different things, so there's no "instead" involved. UNIX is a backronym, based on the MULTICS operating system that UNIX was loosely based on. Misspelling it as a proper noun or a common noun is simple ignorance. UNIX is an operating system, POSIX is a test suite.
spyingwind@reddit
There is a certification process to get the label of POSIX compliant.
As a few example macos, solaris, and z/os are officially certified.
AudioHamsa@reddit
because Unix was a brand which became more popular than posix, the standard.
Samiassa@reddit
They’re two different things. For instance the shell I use is fish, and fish is not posix compliant. It’s certainly unix like, it functions mostly the same as bash and zsh which are posix compliant, but it’s still not actually compliant. So describing it as posix would be wrong even though describing it as “Unix compatible” would be correct
mosskin-woast@reddit
Crazy not to Google posix compliance before posting this
gordonmessmer@reddit
Both Unix and POSIX are trademarks, so you shouldn't use either of them to describe something that isn't licensed to use the term.
Both Unix and POSIX have formal specifications, so neither of them is subjective.
georgehank2nd@reddit
Unix isn't a trademark, UNIX is.
gordonmessmer@reddit
Correct but not terribly relevant. You're not going to get away with using "Unix" on the claim that it isn't the correct capitalization of the trademark.
jqVgawJG@reddit
For the same reason the os is "incorrectly" called Linux
throwaway234f32423df@reddit
I prefer "Linux-like" or perhaps "GNUlike/Linuxlike"
jacob_ewing@reddit
I always liked *nix, but good luck pronouncing it.
GreatBigBagOfNope@reddit
Because there are things that are UNIX-like which have not been certified as POSIX-compliant
Fuckspez42@reddit
I’ve never really thought about this, but I’ll wager it has to do with how Linux (and the language around it) was initially distributed.
Microsoft existed in a world of big, heavy, cryptic user manuals. In the early days of the proto-internet, questions on support forums were frequently answered by referring someone to a specific page/topic in the manual.
Linux, OTOH, existed in a world of NNTP Newsgroups and pre-Google websites that you just needed to know the address of, since search engines were still in their infancy.
It’s not surprising that the less-precise language prevailed in this space.
Also, true POSIX-compliancy is often a pipe-dream; it’s too specific to be seen as a reasonable goal nowadays.
Bulkybear2@reddit
Eh I just like a good os. Idc if it’s posix or not. When I was younger I was all about hey this is posix compliant mostly, nice. Then somewhere along the way I just started feeling like it doesn’t matter tbh.
Chester-Berkeley@reddit
Unix-like and POSIX are not the same. Linux itself is Unix-like but it is not POSIX, because the Linux kernel is similar to the Unix kernel, but it does not strictly follow POSIX like BSDs and other software.
guzzijason@reddit
POSIX is a standard. Unix or Unix-like refers to an OS, which may or may not meet POSIX compliance. It’s like say f we should refer to toasters or toaster-like appliances as “UL”, or that ladders or ladder-like devices be called “OSHA”.
nacaclanga@reddit
Not all unix-like systems actually conform to the POSIX standard. Linux for example does not (at least not fully). For many things this is irrelevant. The POSIX standard is also younger then the concept of a Unix-like system.
Unix-like is intentionally a bit vague.
TerribleReason4195@reddit
It is because I do not know what POSIX means, but I know about the Unix operating system. Unx-like operating systems copy a lot of things from Unx.
finlay_mcwalter@reddit
There's lots of components that are common to modern Unix-like systems that aren't specified by POSIX. X, and now Vulcan aren't. Neither is Gnome/GTK not KDE/Qt.Nor subsystems like CUPS, Pipewire, and systemd. POSIX doesn't specify packages or software delivery (apt, snap, flatpack, pacman), virtualisation (Xen, VirtualBox, QEMU), containerization (e.g. Docker), or orchestration (e.g. Kubernetes).
So a bare POSIX-only OS is a bare-bones thing indeed, with little of the capabilities needed either for a modern desktop or modern server environment.
i80west@reddit
Because Unix was first and started it all.
shadowolf64@reddit
Probably because most Linux distros aren't actually POSIX certified (outside a few specific cases) and instead aim for mostly POSIX compliant. I don't know the specifics, but my understanding is some specific POSIX semantics fails on a number of Linux distros.
Also I think Unix is just in the vocabulary of this space and sticks around because people understand what you mean if you say Unix vs people having to look up what POSIX means.
Jumpy-Dinner-5001@reddit
Most don't even know what they're talking about. They do because they think it sounds cool or edgy.
It's one of those examples where newer or lesser educated users (which is not bad or anything) talk about something they think matters, often because their favorite influencers do it as well, despite not really understanding why or why it matters.
Those who do, rarely talk about that stuff.
-whats-that-meow-@reddit
Because they are two different things.
mckenzie_keith@reddit
Posix is not unix. Many things that are posix compliant or somewhat compliant, are not unix at all. The entire idea underlying your question is completely wrong.
gordonnowak@reddit
because nothing actually conforms to POSIX. so that would be a lie