I am looking for official documents on all POSIX standards and specifications. I would like to be able t read the docs to get a better understanding of UNIX systems and how they work at a low level. I've seen links here and there to opengroup.org, which I'm assuming is the entity behind the standards (however, I've heard IEEE mentioned a lot too).

For a good rundown of POSIX, see this question: What exactly is POSIX? It answered a lot of questions for me.

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    Sorry but Posix.1 will not give you a better understanding of how Unix systems work at a low level. The standard only covers a small "portable' subset of the commands and APIs on a Unix platform.
    – fpmurphy
    Aug 31, 2011 at 14:04

2 Answers 2


POSIX 2008


In addition to the web links, you can also install the POSIX man pages, e.g. on a Debian-like system they are available as manpages-posix-dev package.

Then you can lookup the POSIX version of say - the read system call - via:

$ man 3p read

Or the mv command

$ man 1p mv

Just add a p to the usual man page section number.

'to get a better understanding of UNIX' perhaps some books are better suited than the POSIX specification, e.g. 'Advanced Programming in the UNIX environment' (from a developer centric view) and various 'The Design and Implementation of X', 'Y Internals' or Linux kernel books (from a kernel architecture centric view).


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